Luminal stenting

ABSTRACT

A stent delivery system can include a core member, first and second restraints, and a stent engagement component. The core member can have a distal segment. The first and second restraints can be coupled to the core member distal segment and axially spaced apart from each other to provide an axial gap. The first and second restraints can each have an outer profile that tapers radially inwardly in directions away from the gap. The stent engagement component can be at least partially disposed in the axial gap between the first and second restraints such that the component is slidably and rotatably coupled to the core member distal segment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/754,766, filed Jun. 30, 2015, which is a continuation of U.S. patentapplication Ser. No. 14/040,501, filed Sep. 27, 2013, now U.S. Pat. No.9,072,624, which claims the benefit of U.S. Provisional Application No.61/870,755, filed Aug. 27, 2013. U.S. patent application Ser. No.14/040,501, filed Sep. 27, 2013, now U.S. Pat. No. 9,072,624 is also acontinuation-in-part of U.S. patent application Ser. No. 13/692,021,filed Dec. 3, 2012, now U.S. Pat. No. 8,591,566, which claims thebenefit of U.S. Provisional Patent Application No. 61/602,567, filedFeb. 23, 2012, and U.S. Provisional Patent Application No. 61/679,106,filed Aug. 3, 2012. The entireties of each of the foregoing priorapplications and patents are incorporated herein by reference.

BACKGROUND

Walls of the vasculature, particularly arterial walls, may develop areasof pathological dilatation called aneurysms. As is well known, aneurysmshave thin, weak walls that are prone to rupturing. Aneurysms can be theresult of the vessel wall being weakened by disease, injury, or acongenital abnormality. Aneurysms could be found in different parts ofthe body, and the most common are abdominal aortic aneurysms and brainor cerebral aneurysms in the neurovasculature. When the weakened wall ofan aneurysm ruptures, it can result in death, especially if it is acerebral aneurysm that ruptures.

Aneurysms are generally treated by excluding the weakened part of thevessel from the arterial circulation. For treating a cerebral aneurysm,such reinforcement is done in many ways including: (i) surgicalclipping, where a metal clip is secured around the base of the aneurysm;(ii) packing the aneurysm with small, flexible wire coils (micro-coils);(iii) using embolic materials to “fill” an aneurysm; (iv) usingdetachable balloons or coils to occlude the parent vessel that suppliesthe aneurysm; and (v) intravascular stenting.

Intravascular stents are well known in the medical arts for thetreatment of vascular stenoses or aneurysms. Stents are prostheses thatexpand radially or otherwise within a vessel or lumen to provide supportagainst the collapse of the vessel. Methods for delivering theseintravascular stents are also well known.

In conventional methods of introducing a compressed stent into a vesseland positioning it within in an area of stenosis or an aneurysm, aguiding catheter having a distal tip is percutaneously introduced intothe vascular system of a patient. The guiding catheter is advancedwithin the vessel until its distal tip is proximate the stenosis oraneurysm. A guidewire positioned within an inner lumen of a second,inner catheter and the inner catheter are advanced through the distalend of the guiding catheter. The guidewire is then advanced out of thedistal end of the guiding catheter into the vessel until the distalportion of the guidewire carrying the compressed stent is positioned atthe point of the lesion within the vessel. Once the compressed stent islocated at the lesion, the stent may be released and expanded so that itsupports the vessel.

SUMMARY

At least one aspect of the disclosure provides methods and apparatusesfor delivering an occluding device or devices (e.g., stent or stents) inthe body. The occluding device can easily conform to the shape of thetortuous vessels of the vasculature. The occluding device can be used ina variety of applications. For example, in some embodiments, theoccluding device can direct the blood flow within a vessel away from ananeurysm. Additionally, such an occluding device can allow adequateblood flow to be provided to adjacent structures such that thosestructures, whether they are branch vessels or oxygen demanding tissues,are not deprived of the necessary blood flow.

The delivery of an intravascular stent to a treatment site within thevessel of a patient requires substantial precision. Generally, duringthe implantation process, a stent is passed through a vessel to atreatment location. The stent can be expanded at the treatment location,often by allowing a first end of the stent to expand and thereafterslowly expanding the remainder of the stent until the entire stent hasbeen expanded. The process of initially contacting the vessel wall asthe first end of the stent expands can be referred to as “landing” thestent. The final position of the stent within the vessel is generallydetermined by its initial placement or landing within the vessel. Insome situations, the stent may initially be “landed” in a suboptimallocation within the vessel. Using traditional methods and apparatuses,it may be very difficult for a clinician to reposition the stent withinthe vessel. For example, a clinician may be unable to recapture,collapse, withdraw, or resheath the stent back into the catheter afterthe stent has been partially expanded within the vessel. As such, theinitial landing is critical to successful placement of the stent.

In accordance with an aspect of at least some embodiments disclosedherein is the realization that a medical device delivery system can beconfigured to advantageously enable a clinician to recapture, collapse,withdraw, or resheath a stent within a catheter of the delivery systemafter the stent has been at least partially expanded and landed in thevessel in order to allow the clinician to improve the placement of thestent within the vessel. Further, some embodiments can be configured toenable a clinician to recapture, collapse, withdraw, or resheath thestent even the entire stent has been moved out of the catheter lumen andat least partially expanded against the vessel wall. Moreover, someembodiments can be provided such that the delivery system can engage andretain any braided stent without requiring special-purpose engagementstructures on the stent.

Some embodiments of the system can enable a clinician to advance,recapture, collapse, withdraw, or resheath a stent within a patient'svasculature. According to some embodiments, the system can comprise acore member for moving, either by distally advancing or proximallyretracting, a stent within a body lumen. The core member can beconfigured to extend within a sheath, microcatheter, or tube of thedelivery system. The system can comprise a core assembly that isslidably disposed within a catheter and able to secure, grip, or engageat least a portion of the stent in order to control movement,deployment, and expansion of the stent.

In some embodiments, the system can compress the stent against an innerwall of a catheter or lumen. The system can optionally comprise anengagement component, protruding member, stop member or restraint,sleeve, bumper, or variable dimension portion providing aradially-extending dimension, disposed along the core member. Theengagement component can provide compressive engagement of the stentagainst an inner wall of the catheter or lumen.

In some embodiments, the core assembly can comprise a constrainingmember and a core member. The stent can extend over the core member andinto a recess formed by the constraining member to engage or secure aportion of the stent. Some embodiments can be configured such that theconstraining member engages a proximal portion of the stent.

Optionally, the core assembly can also comprise an engagement component,protruding member, stop member or restraint, sleeve, bumper, or variabledimension portion providing a radially-extending dimension, disposedalong the core member. In such embodiments, the stent can extend overthe engagement component and into the recess.

For example, the engagement component and the constraining member cancollectively form a gripping mechanism that engages or secures thestent. The gripping mechanism can engage a proximal or first portion ofthe stent in a collapsed state. The gripping mechanism can provide apress or interference fit between the constraining member and theengagement component to inhibit expansion of the first end of the stent.The gripping mechanism can enable the stent to be withdrawn, recaptured,retracted, or resheathed into the catheter even after the stent has beenmoved out of the catheter lumen (i.e., the catheter has been fullywithdrawn from the stent) and the stent has at least partially expandedinto apposition with the vessel wall.

The gripping mechanism can enable the core assembly to exert a pushingforce and a pulling force on the stent to adjust its axial positionrelative to the catheter. In some embodiments, the gripping mechanismcan be operative to exert a distal pushing force on the stent todistally advance the stent relative to the catheter until the firstportion of the stent is distally beyond the distal end of the catheter.Further, the gripping mechanism can also be operative to exert aproximal pulling force on the stent to proximally withdraw the stentinto the catheter when the stent first portion is distally beyond thedistal end of the catheter and the stent is at least partially expandedinto apposition with a vessel wall. The gripping mechanism can beconfigured to exert the distal pushing force and the proximal pullingforce on its own without the cooperation of other components orstructures.

In some embodiments, the stent can be secured or engaged between theengagement component and a distal end of the constraining member (whichcan be a sheath) in order to prevent expansion of a proximal or firstportion of the stent. For example, the engagement component and theconstraining member can secure the stent by inducing a variable diameterin the stent between the first portion and the second portion.

In some embodiments, the assembly can be configured such that the coremember has a distal section and a proximal section. The distal sectionof the core member can be a distal tapering section. The core member cancomprise a wire. For example, the distal section of the core member cancomprise a distal tip. The core member distal tip can comprisepolytetrafluoroethylene (PTFE or TEFLON®).

The constraining member can have an inner lumen that is configured toreceive the core member. Further, the constraining member can have adistal portion that can be spaced apart from the core member and canhave a capture area in the lumen. The capture area can be definedbetween the distal portion of the constraining member and the coremember. For example, the capture area can be defined radially between anouter surface of the core member and an inner surface of the tubularconstraining member.

Further, the engagement component can be disposed along the core memberat least partially distal of the capture area. In some embodiments, theengagement component can extend continuously around the core member.However, the engagement component can also extend around only a portionof the core member. The engagement component can also extend radially.Further, the engagement component can have an outer surface. In someembodiments, the engagement component can be disposed axially betweenthe distal section and the proximal section of the core member.Furthermore, the stent can have a first portion and a second portion.The first portion can be a proximal portion that is disposed within thecapture area. The second portion can be disposed distal relative to thefirst portion. The second portion can extend across or over an outersurface of the engagement component so that the engagement component andthe constraining member cooperate to inhibit expansion of the firstportion of the stent.

In some embodiments, the core member can extend within the stent lumenand distally beyond a second portion of the stent. The engagementcomponent can be coupled to the core member and be disposed distal ofthe distal portion of the constraining member within the stent secondportion.

The engagement component can optionally have a generally cylindricalouter surface. For example, the engagement component can comprise anannular ring or sleeve coupled to or supported on the core member. Theouter surface of the engagement component can be radially offset fromthe outer surface of the core member. Further, the engagement componentcan be axially spaced apart from the distal portion of the constrainingmember. For example, the outer surface of the engagement component canbe radially offset from the inner surface of the constraining member.Furthermore, the outer surface of the engagement component can beradially offset from the capture area is defined by the constrainingmember and the core member. In some embodiments, the outer surface ofthe engagement component can be spaced radially between the outersurface of the core member and the inner surface of the constrainingmember. Furthermore, the second portion of the stent can extend over orbe supported on the outer surface of the engagement component.

The engagement component can be disposed at least partially distal ofthe distal portion of the constraining member. Further, when theassembly is oriented substantially straight, the engagement componentcan be configured such that it does not press the stent against theinner surface of the catheter.

The engagement component can also have an outer surface that is radiallyspaced apart from the inner surface of the catheter such that when theassembly is oriented substantially straight, the engagement componentdoes not press the stent against the inner surface of the catheter. Forexample, the engagement component can have a generally cylindrical outersurface. Further, when the assembly is oriented substantially straight,a radial distance between the outer surface of the engagement componentand the inner surface of the catheter can be sized greater than athickness of the stent.

However, in accordance with some embodiments, the engagement componentcan be configured to compress the stent against an inner wall of thesheath, catheter, or tube. In such embodiments, the engagement betweenthe engagement component and the stent can be used to move the stentwithin the sheath, catheter, or tube without the use of a constrainingmember. As noted herein, the engagement component can be fixed relativeto the core member (i.e., not rotatable or translatable relative to thecore member) or can be configured to rotate and/or translate relative tothe core member to provide advantages such as those discussed herein.

Additionally, in some embodiments, the catheter can be provided in orderto form a stent delivery system. The stent delivery system can comprisethe catheter and a core assembly. The catheter can have a distal end. Asnoted above, the core assembly can comprise a tubular constrainingmember, a stent, a core member, and a radially extending engagementcomponent.

In accordance with some embodiments, the constraining sheath can includea lumen having a cross-sectional inner profile. The engagement componentcan have a cross-sectional outer profile that is sized about equal to orgreater than the catheter inner profile. The cross-sectional outerprofile of the engagement component can be sized greater than thecatheter inner profile. The stent can extend over the engagementcomponent and into the constraining sheath such that the stent has afirst diameter at the stent's first portion and a second diameter at thestent's second portion, sized greater than the first diameter. Thus, thestent can be secured between the engagement component and the sheathdistal end. In accordance with some embodiments, the engagementcomponent can be rotatably mounted on the core member, as discussedfurther herein. Further, the engagement component and the core membercan also be formed from a continuous piece of material.

Further, a collective outer profile of the stent and the proximal membercan be sized greater than the sheath inner profile. The core member canbe configured to be steerable when a distal end of the stent is expandedinto contact with a blood vessel by being rotatable relative to thestent and the constraining sheath. In some embodiments comprising anengagement component, the core member can also be rotatable relative tothe engagement component.

The delivery of a stent in a vessel and subsequent expansion of thestent into apposition with the vessel wall can present some challengesin tortuous vessels. For example, during delivery to the treatment site,the delivery system can be configured to comprise one or more rotatablecomponents that allow components of the system to rotate relative toeach other while the delivery system traverses tortuous geometries. Suchflexibility can reduce the overall pushing force required and tend toavoid “whipping” of the stent when it is unsheathed and/or expanded intothe vessel.

For example, in accordance with some embodiments, the delivery systemcan comprise a rotatable core assembly. In such embodiments, the coremember can rotate independently of the engagement component (if present)and/or the stent and the constraining member within the catheter toreduce “whipping” and also to enable steering of the core member, asdiscussed further herein. Such rotatability can facilitate the movementof the core assembly through a catheter of the delivery system so as toreduce the delivery force required to reach the treatment site.

Further, the rotatable core assembly can be configured to allow the coremember to rotate independently of the stent being deployed in thevessel. Thus, the protruding end of the core member can be rotatedwithout disrupting the contact between the vessel wall and the stent.Thus, the clinician can rotate a distal, protruding end of the coremember to preferentially align the protruding end with the adjacentvessel geometry to avoid abrading or perforating the vessel wall whileadvancing the assembly.

For example, after the stent has been moved to the treatment site, thecore member of the delivery system may often include a distallyprotruding end that may be displaced distally as the stent is expandedand released. The distal movement of the protruding end represents ahazard of potentially abrading or perforating a wall of the vessel inwhich the stent is being delivered. Further, when the stent is beingdelivered adjacent to a vessel bifurcation or a sharp turn in thevessel, the vessel geometry, such as an apex of the bifurcation, may beparticularly difficult to avoid.

In some embodiments, a core assembly can be rotatable by providing anengagement component that is rotatably positioned about the core memberand rotatably coupled to or mounted on the core member. In suchembodiments, the core member can be rotatably coupled relative to theengagement component thereof in order to allow the core member to rotaterelative to the engagement component, the constraining member, and thestent. For example, the engagement component can comprise an annularcomponent or sleeve that is rotatably mounted on the core member.

Thus, a rotatable (and in some embodiments, steerable) stent deliverysystem can be provided. Embodiments of such a system can comprise amicrocatheter, a core member, and a stent. The microcatheter can have adistal end configured to be inserted into a blood vessel. The coremember can extend within the microcatheter. Further, the core member canhave a distal portion and an intermediate portion proximal to the distalportion. The stent can extend along the intermediate portion. Further,the core member can be configured to be steerable when a distal end ofthe stent is expanded into contact with the vessel by being rotatablerelative to the stent and the microcatheter. Accordingly, the coremember can be steerable to avoid dislodging of the stent from the vesselwall and abrading or perforation of the vessel wall.

In some embodiments wherein the system comprises an engagementcomponent, the engagement component can be positioned along the coremember in the intermediate portion and be rotatably coupled to the coremember. In some embodiments, the core member can comprise an arcuate tipthat extends distal of the engagement component. The core member distalportion can comprise the arcuate tip, which can extend transverse to alongitudinal axis of the microcatheter. The arcuate tip can extendtransverse to or bends away from a central axis of the microcatheterlumen. The microcatheter can be either as the constraining sheath orcatheter discussed herein.

In some embodiments, the distal portion can comprise an assemblyincluding the distal cover and a distal tip structure. The tip structurecan be rotatably or fixedly coupled relative to the core member.Further, the distal cover can be coupled to the tip structure.

The distal tip structure can comprise at least one member or componentthat can be carried by the core member. In some embodiments, the atleast one member can be oriented generally transverse or parallel to thecore member. For example, the tip structure can comprise a coil(s), acircumferentially-extending band(s) of material, a clamp(s), and/orother structures that can pass smoothly within a vessel at the distalportion of the core member. Further, the at least one member cancomprise at least one segment of the coil or other structure.

In some embodiments of a rotatable core assembly, the distal portion ofthe core member can comprise a distal tip structure and/or distal coverthat can be rotatably coupled to the core member. Thus, a rotatableinterconnection between the distal tip structure and/or distal cover andthe core member can allow the core member to rotate freely of the distaltip structure and/or distal cover, thus avoiding transmission of anyrotational or torsional stresses to the stent via the distal cover. Forexample, the distal cover can be configured to rotate about the coremember. Further, the second end of the distal cover can be rotatablycoupled with respect to the core member. Furthermore, the stent can beconfigured to rotate about the core member at least in part by virtue ofthe rotatable coupling of the distal cover.

In operation, after the catheter has been positioned in the bloodvessel, the stent can be partially expanded into apposition with a wallof the vessel. The clinician can rotate a distalmost curvilinear tip ofthe core member of the delivery system. The tip can be configured tobend away from a central longitudinal axis of the core member. Thus,when rotated, the core member's curvilinear tip can rotate relative tothe stent and the constraining member. Further, as noted above in someembodiments comprising an engagement component, the core member can berotatably coupled to the engagement component. In such embodiments, whenrotated, the core member's curvilinear tip can rotate relative to thestent, the engagement component, and the constraining member.Accordingly, the clinician can align the curvilinear tip with a path ofthe vessel to avoid abrading or perforating the vessel wall. Thereafter,the core member can be advanced distally to guide the core member alonga path of the vessel. Such methods and systems can be particularlyuseful when the geometry of the vessel includes a bifurcation or a sharpturn in the vessel, especially to guide the tip of the core member awayfrom an apex of a bifurcation adjacent to the treatment site.

In accordance with yet other embodiments disclosed herein, the coreassembly can be configured to comprise a distal portion that enables adistal or leading end of the core assembly and stent to be lubriciouslypassed through a catheter while also facilitating the resheathing of thedistal portion within the catheter, as desired.

In some embodiments in which the distal portion comprises a distalcover, the distal cover can be coupled to the core member and at leastpartially surround or cover the stent second portion. Thus, when thecore assembly is slidably disposed within the catheter, the distal covercan be positioned between, for example, radially between, the stentsecond portion and the catheter inner wall.

In embodiments that comprise a distal cover, the distal cover cancomprise a flexible material that can extend anteriorly over at least aportion of the stent in order to provide a lubricious interface betweenthe core assembly and an inner surface of the catheter lumen.

The distal cover can be attached are coupled to the distal tip structureor core wire using a variety of attachment means. According to someembodiments, the distal cover can be coupled to the distal tip structureby virtue of forming an enclosure that encloses at least one member ofthe distal tip structure. For example, the distal cover can form anenclosure that encloses the tip structure, e.g., at least one coilsegment, by virtue of at least partially wrapping around the segment.

The distal cover can comprise one or more elongate strips of material.For example, the distal cover can comprise a pair of a longitudinallyextending elongate strips that at least partially cover or surround thesecond portion of the stent. In some embodiments, the distal covercomprises no more than two elongate strips of material. In someembodiments, the distal cover can be cut from a tubular member such thata plurality of elongate strips are formed and interconnected by anannular ring of material.

Further, the distal cover can be configured to allow the distal end ofthe stent to expand when the distal end of the stent is moved axiallybeyond a distal end of the catheter. In some embodiments, the distalcover can be configured to provide little or no constraining force orotherwise inhibit the expansion of the distal end of the stent.

The distal cover can be configured to flip, evert, or otherwise movefrom one position to another. In accordance with some embodiments, thedistal cover can comprise a first end and a second end. The first endcan be a free first end, and the second end can be coupled to the distalportion. The distal cover can have a first, delivery, or proximallyoriented position, orientation, or configuration in which the first endextends proximally relative to the core member distal portion and atleast partially covers or surrounds the stent second portion. The distalcover can be movable from the first, delivery, or proximally orientedposition, orientation, or configuration, in which the free first end islocated proximally relative to the second end, to a second, resheathing,everted, or distally oriented position, orientation, or configurationwherein the first end is positioned distally relative to the second end.Thus, the distal cover can enable the core assembly to be easilywithdrawn or received into the catheter lumen. Further, the distalportion of the constraining member can be axially spaced apart from adistal portion of the stent in both the delivery position orconfiguration and the resheathing position or configuration.

In some embodiments, the distal cover can extend anteriorly relative tothe attachment point of the distal cover and/or the distal tip structurewhile the stent is being delivered to the treatment site. For example,the distal cover can extend along at least about one third of the stent.Further, the distal cover can be everted to extend distally relative tothe attachment point of the distal cover and/or the distal tip structureafter the distal end of the stent has been expanded.

Various methods for operating the core assembly and the stent deliverysystem are also provided. Initially, in order to position the stentdelivery system within a vessel of a patient, a clinician can firstposition a catheter in the vessel. The catheter can have a lumen thatdefines an axis extending between a proximal end and a distal end, suchthat the catheter distal end is at a treatment site. The clinician canposition a core assembly within the catheter lumen. The clinician canalso advance the core assembly distally within the catheter. Thereafter,various implementations of methods can be performed using one or more ofthe core assemblies disclosed herein.

For example, operation of an embodiment of a stent delivery system canbe performed by first moving a core assembly through a catheter to atreatment site. A constraining member of the assembly can be configuredto receive a portion of a stent first portion, such that the stent issecured between a distal end of the constraining member and a proximalend of an engagement component in a delivery position. The catheter canbe proximally retracted relative to the core assembly until theconstraining member distal end and the stent first portion arepositioned distally beyond a catheter distal end while maintaining thestent first portion in the delivery position or configuration with thecore member distal section extending distally relative to the stent.Further, a distal portion of the stent can be expanded into appositionwith a vessel wall while maintaining the stent first portion in thedelivery position.

Thus, in accordance with some embodiments, the core assembly can beproximally withdrawn into the catheter to resheath the stent within thecatheter after the distal portion of the stent has already beenexpanded. When using a self-expanding stent, a distal portion of thestent can expand automatically when the distal portion of the stentexits the catheter. Further, in order to expand a distal portion of thestent, a distal cover, which at least partially surrounds or covers adistal portion of the stent, can be unfurled.

Additionally, in some embodiments in which the core assembly comprisesthe distal cover, the distal cover can extend in a proximal direction toat least partially cover a distal portion of a stent supported on thecore assembly. At least a portion of the distal cover can be interposedbetween the stent distal portion and the inner wall. The stent distalportion can be distally advanced beyond the catheter distal end topermit expansion of the stent distal portion. The core assembly can thenbe withdrawn into the lumen, such that the distal cover is retractedinto the lumen in an everted configuration and oriented distally fromthe core assembly.

Further, in some embodiments, in which the core assembly has (i) anelongate member comprising a distal end, (ii) an intermediate portioncomprising a distal end positioned at the member distal end, (iii) astent having a distal portion and being carried by the intermediateportion, and (iv) a distal cover coupled to the member distal end, thecore assembly can be positioned within the lumen such that theintermediate portion distal end is positioned axially adjacent thecatheter distal end with at least a portion of the distal coverextending in a space within the lumen radially between the intermediateportion distal end and the catheter distal end. The clinician can thendistally advance the core assembly relative to the catheter to permitexpansion of the stent distal portion. The expansion can urge the distalcover away from the intermediate portion. Finally, the clinician canproximally withdraw the core assembly into the catheter such that theintermediate portion is positioned axially adjacent to the catheterdistal end with the distal cover positioned outside of the space. Insome embodiments, during proximal withdrawal of the core assembly intothe catheter, the distal cover can be positioned outside of the space toprovide a clearance between the intermediate portion and the catheter.

Furthermore, in some embodiments, the core assembly can have (i) adistal portion, (ii) a distal cover extending from the distal portion,and (iii) a stent having a distal portion and being carried by the coreassembly. The core assembly can be advanced within the catheter suchthat the distal cover extends proximally from the distal portion and anannular space between the distal portion and the catheter. The cliniciancan distally advance the core assembly relative to the catheter topermit expansion of the stent distal portion. The expansion can urge thedistal cover radially away from the core assembly. Further, the coreassembly can be proximally withdrawn into the catheter such that thedistal cover extends distally through the annular space. In suchembodiments, during proximal withdrawal of the core assembly into thecatheter, the distal cover can extend distally through the annular spaceto provide a clearance between the catheter and an intermediate portionof the core assembly proximal to the distal cover.

Further, embodiments of the methods can further comprise advancing thecore assembly distally within the catheter such that a proximal end ofthe stent is positioned outside of the lumen. The method can beperformed to further comprise the step of releasing the stent at thetreatment site within the vessel. The method can also compriseproximally withdrawing the core assembly from the lumen whilemaintaining the catheter distal end in place at the treatment site.Additionally, a second core assembly can be inserted into the lumen. Thesecond core assembly can be configured to deliver a second stent at thetreatment site.

In some embodiments of the methods, proximally withdrawing the coreassembly can comprise everting a free first end of the distal cover froma proximally oriented position to a distally oriented position. Further,the distal cover can be coupled to the core assembly at a distal coversecond end, and the first end can be positioned distally relative to thesecond end when the distal cover is everted.

In accordance with yet other embodiments of the methods, the distalcover can comprise a plurality of elongate flexible strips having firstends and second ends. The second ends can be coupled to the coreassembly. In such embodiments, proximally withdrawing the core assemblycan comprise everting the distal cover, such that the first ends aredrawn together distal to the second ends.

In accordance with some embodiments, a rotatable stent delivery systemis provided that can comprise a microcatheter, a core member, at leastone engagement component, and a stent.

In some embodiments, the microcatheter can have a distal end configuredto be inserted into a blood vessel. The core member can extend withinthe microcatheter. The core member can have a distal segment. The atleast one engagement component can comprise a sleeve, which can bepositioned about the core member distal segment and rotatably coupled tothe core member. The stent can extend along the core member distalsegment.

In some embodiments, a proximal end of the stent can be engaged with theconstraining member distal portion and the engagement component orsleeve to restrict movement of the stent relative to the constrainingmember and the engagement component or sleeve while the core member isrotatable relative to the stent, the constraining member, and theengagement component or sleeve. Thus, in some embodiments, the distalportion of the core member can comprise a distal tip structure and/ordistal cover that can be rotatably coupled to the core member, and thesleeve and distal cover can permit rotation of the core member relativeto the stent.

Further, in some embodiments, the microcatheter can have a lumen, andthe constraining sheath can have a distal portion and extend within themicrocatheter lumen. The core member can extend within the microcatheterlumen. The at least one sleeve can be positioned about and rotatablycoupled to the core member. Further, the stent can be self-expanding andhave (i) a proximal or first portion disposed within the sheath lumenand (ii) a distal portion extending over an outer surface of the sleeve,while the core member is rotatable relative to the stent, theconstraining member, and the sleeve.

The microcatheter can comprise a lumen having a central axis, and thecore member distal segment can comprise an arcuate tip that extendstransverse to the axis.

The core member can be rotatable or steerable to avoid (i) dislodging ofthe stent from the vessel wall and (ii) perforation of the vessel wall.The core member can extend within the constraining member or sheath. Insome embodiments, the core member can comprise a delivery wire.

The constraining member or sheath can be disposed along the core memberand a distal portion (i) spaced apart from the core member and (ii)having a capture area. The engagement component or sleeve can bepositioned adjacent to a distal end of the constraining member in anengaged position. The stent can have (i) a first portion disposed withinthe capture area and (ii) a second portion, distal to the first portion,supported on an outer surface of the engagement component or sleeve torestrict movement of the stent relative to the engagement component orsleeve and the constraining member. Further, some embodiments, theconstraining member and the sleeve can cooperate to grip the firstportion or proximal and of the stent.

The system can also comprise a distal cover extending proximally fromthe core member distal segment and interposed between an outer surfaceof the stent and an inner surface of the microcatheter. The system canalso comprise a distal tip attached to the core member at the distalsegment thereof, and the distal cover can be attached to the distal tip.The distal tip can be rotatably coupled to the core member. The distaltip and the core member can be formed from a continuous piece ofmaterial.

The system can further comprise an actuator attached to a proximalportion of the core member, and the actuator can be configured to impartrotation the core member.

In some embodiments, the stent distal portion can be at least partiallycovered at the core member distal segment. The stent can have a firstdiameter at the first portion and a second diameter at the distalportion, sized greater than the first diameter, such that the stent issecured between the engagement component and the sheath distal portion.

The engagement component can have a cross-sectional outer profile thatis sized about equal to or greater than the constraining member innerprofile. In some embodiments, the engagement component can have across-sectional outer profile that is sized greater than theconstraining member inner profile.

The system can be configured such that in a delivery position, the firstportion of the stent is restricted from expansion and restricted frommovement, such as longitudinal movement, relative to the engagementmember and the sheath distal portion. Further, a collective outerprofile of the stent and the engagement component can be sized greaterthan the sheath inner profile.

The core member can be rotatable relative to the stent and themicrocatheter when the stent is partially expanded within the vessel.For example, the engagement component outer profile can be generallycylindrical. The engagement component can comprise a tubular structurefitted over the core member. The constraining sheath can comprise adistal portion (i) spaced apart from the core member and (ii) having acapture area. Optionally, an outer surface of the engagement componentcan be radially offset from the capture area. The stent can be engagedbetween the engagement component and the constraining sheath in a pressfit to prevent expansion of the stent first portion. The stent can beengaged between the engagement component and the constraining sheath inan interference fit to prevent expansion of the stent first portion.

According to some embodiments, the stent delivery system can comprise acore member and first and second restraints for restraining movement ofa stent engagement component therebetween. The core member can have adistal segment. The first and second restraints can be coupled to thecore member distal segment and axially spaced apart from each other toprovide an axial gap. The first and second restraints can each have anouter profile that tapers radially inwardly, in directions away from thegap. For example, the first restraint can taper in a distal directionand the second restraint can taper in a proximal direction. Further, thestent engagement component can be, for example, a stent cover componentor a stent engagement or support member.

In some embodiments, the first restraint can be positioned distally ofthe second restraint. The first and second restraints can have differentmaximum outer cross-sectional profiles. For example, the first restraintcan have an outer profile that is less than an outer profile of thesecond restraint. The first restraint can have a maximum outer diameterless than a maximum outer diameter of the second restraint. The firstrestraint can have a maximum outer diameter less than a maximumcross-sectional profile of the stent cover component.

In some embodiments, the stent engagement component can be at leastpartially disposed in the axial gap between the first and secondrestraints such that the component is slidably and rotatably coupled tothe core member distal segment. The stent engagement component can beformed separately from the core member such that it can rotate about andslide along the core member between the restraints. The first and secondrestraints can have maximum outer cross-sectional profiles that are lessthan a maximum diameter of the stent engagement component. The systemcan also comprise a stent, carried by the core member, that can have aninner diameter that is greater than maximum cross-sectional profiles ofthe first and second restraints.

Additionally, the stent engagement component can be a stent engagementor support member that is rotatably coupled to the core member distalsegment in the gap between the first and second restraints. The firstand second restraints can have maximum outer cross-sectional profilesthat are less than a maximum diameter of the stent engagement or supportmember.

In some embodiments, the stent engagement component can be a stent covercomponent having a first end positioned in the axial gap between thefirst and second restraints such that the first end is rotatably coupledto the core member distal segment. The stent cover component can have atleast one second end extending from the first end. The at least onesecond end can be configured to at least partially surround at least adistal portion of a stent carried by the stent delivery system. Thefirst end of the stent cover component can be formed separately from thecore member such that the first end is rotatable about and slidablealong the core member between the first and second restraints.

Some embodiments of the system can further comprise third and fourthrestraints and a stent engagement member. The third and fourthrestraints can be rotatably coupled to the core member distal segmentand axially spaced apart from each other to provide a second axial gap.Another stent engagement component (e.g., a stent engagement or supportmember or a stent cover component) can be rotatably coupled to the coremember distal segment in the second axial gap between the first andsecond restraints.

The stent engagement component can be formed separately from the coremember such that it can rotate about and slide along the core memberbetween the third and fourth restraints. The engagement component canalso have a maximum outer diameter that is greater than maximumcross-sectional profiles of the third and fourth restraints.

In addition, the system can further comprise a stent positioned over andengaged by the stent engagement member or at least partially enclosedwithin the stent cover component such that the stent is freely rotatableabout the core member. The stent can have an inner diameter that isgreater than maximum cross-sectional profiles of the third and fourthrestraints.

In some embodiments, the axial gap has an axial length of between about0.30 mm and about 0.70 mm greater than an axial length of the stentengagement component. In some embodiments, the axial gap has an axiallength of between about 0.50 mm and about 0.70 mm greater than an axiallength of the stent engagement component. For example, the axial lengthof the axial gap can be about 0.60 mm greater than an axial length ofthe stent engagement component. Further, the second axial gap can havean axial length that is between about 0.30 mm and about 0.50 mm greaterthan an axial length of the stent engagement component. For example, theaxial length of the second axial gap can be about 0.40 mm greater thanthe axial length of the stent engagement component.

The system can also comprise an introducer sheath having a lumenconfigured to receive the core member, the first and second restraints,and the stent cover component.

In some embodiments, the delivery system can comprise a first radiopaquemarker and the catheter can comprise a second radiopaque marker. Thefirst and second radiopaque markers can be longitudinally movablerelative to each other and longitudinally alignable with each other suchthat the system achieves a pre-release position beyond which additionaldistal advancement of the core member permits release of a stent fromthe delivery system. Further, the first restraint can comprise the firstradiopaque marker, and a distal portion of the catheter can comprise thesecond radiopaque marker. The second radiopaque marker can be positionedat the catheter distal end. The first restraint can be positioneddistally of the second restraint.

Methods of operating a rotatable stent delivery system, such as one ofthe systems disclosed herein, can also be provided. For example, thedelivery system can comprise a stent, a constraining member, a coremember or wire having a central longitudinal axis, and an engagementcomponent or sleeve that is rotatably coupled to the core wire. Thestent can extend over the engagement component and be restricted frommovement, such as longitudinal movement, relative to the engagementcomponent and the constraining member. The core wire can thus berotatable relative to the stent, the engagement component, and theconstraining member.

In accordance with some aspects of methods disclosed herein, a cliniciancan advance a distal end of a catheter of the delivery system in a bloodvessel. Further, the clinician can advance the delivery system withinthe catheter. The clinician can advance the core wire distally to guidethe delivery system along a path of the vessel.

The clinician can also move or partially expand the stent of thedelivery system into apposition with a wall of the blood vessel. Theclinician can rotate the core member relative to the other components ofthe core assembly.

For example, the clinician can rotate a distalmost curvilinear tiprelative to the stent, the engagement component, and the constrainingmember. The clinician can rotate the tip, for example, via the core wireor member, until the tip achieves a desired orientation relative to theblood vessel geometry. Thereafter, the clinician can continue to advancethe core wire distally to guide the core wire along a path of thevessel.

In some embodiments, when the clinician rotates the tip, for example,via the core wire or member, the relative movement between the core wireand the stent can avoid dislocation of the stent from the vessel wall.Further, in some embodiments, the clinician can advance the tip toward avessel bifurcation. Furthermore, in some embodiments, the method can beimplemented wherein rotating the tip comprises directing the tip in adirection away from an apex of the bifurcation.

In accordance with some embodiments, a method of delivering a stentdelivery system is also provided that can comprise: inserting thedelivery system into a curved path, the delivery system comprising acatheter, a core member disposed within the catheter, first and secondrestraints coupled to the core member, a stent engagement componentcoupled to the core member between the first and second restraints, anda stent having a first portion (i) supported on the stent engagementcomponent and (ii) extending over at least one of the first and secondrestraints, the first and second restraints each having a longitudinallytapered end. The core member can be caused to bend in the curved path,more than the core member could if the first and second restraints werenot tapered, without causing the first and second restraints to compressthe stent against an inner wall of the catheter.

In accordance with some embodiments of methods disclosed herein, thefirst restraint can be positioned distally of the second restraint, andthe core member can be advanced until the first restraint is determinedto be positioned adjacent to the distal end of the catheter.Additionally, the axial position of the core member can be held ormaintained relative to the catheter, when the first restraint isdetermined to be positioned adjacent to the distal end of the catheter,until initial placement of the stent is determined to be correct.

Further, in some embodiments, the delivery system can comprise a firstradiopaque marker and the catheter can comprise a second radiopaquemarker longitudinally movable relative to the first radiopaque marker.In such embodiments, the first and second radiopaque markers can belongitudinally aligned such that the system achieves a pre-releaseposition beyond which additional distal advancement of the core memberpermits release of the stent from the delivery system. Some embodimentscan be configured such that the first restraint comprises the firstradiopaque marker and a distal portion of the catheter comprises thesecond radiopaque marker. The method can then comprise observing animage of the first radiopaque marker and the second radiopaque marker asthe core member is advanced relative to the catheter. Further, when thesecond radiopaque marker is positioned at the catheter distal end, andthe first restraint can be longitudinally aligned with the catheterdistal end. Further, the first and second restraints can be advanceddistally of the catheter distal end such that the stent first portion isreleased and the stent is disengaged from the delivery system.

In some embodiments of methods disclosed herein, the stent first portioncan undergo a bend of at least about 30°. Some embodiments of themethods can be implemented to cause the stent first portion to undergothe bend without causing the first and second restraints to contact aninner surface of the stent. The stent first portion can be caused toundergo a bend of at least about 45° without causing the first andsecond restraints to compress the stent against the inner wall of thecatheter. The stent first portion can be caused to undergo the bendwithout causing the first and second restraints to contact an innersurface of the stent. The stent first portion can be caused to undergo abend of at least about 60° without causing the first and secondrestraints to compress the stent against the inner wall of the catheter.The stent first portion can be caused to undergo a bend of at leastabout 90° without causing the first and second restraints to compressthe stent against the inner wall of the catheter. The stent firstportion can be caused to undergo a bend of at least about 110° withoutcausing the first and second restraints to compress the stent againstthe inner wall of the catheter.

Methods can also be implemented such that the delivery system furthercomprises third and fourth restraints coupled to the core memberdistally of the first and second restraints. The third and fourthrestraints can be spaced apart to provide a gap wherein a first end of astent cover component is coupled to the core member. The stent firstportion can extend over the first, second, and third restraints. In suchembodiments, the stent first portion can be caused to undergo the bendwithout causing the first, second, and third restraints to compress thestent against the inner wall of the catheter. Further, the stent firstportion can be caused to undergo the bend without causing the first,second, and third restraints to contact an inner surface of the stent.According to such advantageous implementations and methods, the coremember and the stent can be advanced through various tortuouspassageways, such as vessels within the patient or a catheter in atorturous configuration. For example, the core member and the stent canbe advanced through the aortic arch without causing restraints tocompress the stent against the inner wall of the catheter.

Additionally, some embodiments of methods disclosed herein can beimplemented in delivery systems that comprise one or more radiopaquemarkers. For example, the delivery system can comprise a firstradiopaque marker and the catheter can comprise a second radiopaquemarker. The first and second radiopaque markers can be longitudinallymovable relative to each other and longitudinally alignable with eachother such that the system achieves a pre-release position beyond whichadditional distal advancement of the core member permits release of astent from the delivery system. The relative movement of the radiopaquemarkers can signal the location and/or deployment position of the stentto the clinician. For example, the markers can signal the stent isapproaching the target site. Further, the markers can signal that thestent distal end is beginning to extend beyond a distal end of thecatheter. Furthermore, the markers can also signal that the stentproximal end is approaching or about to exit the catheter.

Some embodiments of the system can be configured such that the firstrestraint comprises a first radiopaque marker and a distal portion ofthe catheter comprises a second radiopaque marker. For example, thesecond radiopaque marker can be positioned at the catheter distal end,and the first restraint can be positioned distally of the secondrestraint. Accordingly, as the first radiopaque marker approaches thesecond radiopaque marker during distal advancement of the core assemblywithin the catheter, the clinician can visually determine a position ofthe stent or core assembly relative to a distal end of the catheter.This visual determination can provide further information to theclinician during the deployment operation. For example, the cliniciancan adjust or more parameters of the advancement, such as the speed orposition of the system within the vasculature, or facilitate resheathingof the stent, if necessary.

Additional features and advantages of the subject technology will be setforth in the description below, and in part will be apparent from thedescription, or may be learned by practice of the subject technology.The advantages of the subject technology will be realized and attainedby the structure particularly pointed out in the written description andembodiments hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding of the subject technology and are incorporated in andconstitute a part of this specification, illustrate aspects of thedisclosure and together with the description serve to explain theprinciples of the subject technology.

FIG. 1 is a schematic, partial cross-sectional view of a stent deliverysystem, according to one or more embodiments disclosed.

FIG. 2 is a schematic side view of a core assembly of the system shownin FIG. 1 with a stent mounted thereon, according to some embodiments.

FIG. 3A is a schematic side cross-sectional view of a proximal portionof the core assembly shown in FIG. 2, according to some embodiments.

FIG. 3B is a schematic side cross-sectional view of a proximal portionof the core assembly shown in FIG. 2, according to some embodiments.

FIG. 4A is a schematic side cross-sectional view of an embodiment of acore assembly.

FIG. 4B is a schematic side cross-sectional view of another embodimentof a core assembly.

FIG. 5A is a schematic side cross-sectional view of a distal portion ofthe core assembly shown in FIG. 2, according to some embodiments.

FIG. 5B is a schematic side cross-sectional view of another embodimentof a distal portion of the core assembly shown in FIG. 2.

FIG. 5C is a rear perspective view of yet another embodiment of a distalportion of the core assembly shown in FIG. 2.

FIG. 6 is a schematic side view of the core assembly of the system ofFIG. 1 wherein the stent is not shown, according to some embodiments.

FIG. 7 is a side, cross-sectional view of a medical device deliverysystem disposed within a body lumen, according to some embodiments.

FIG. 8 is an enlarged side, cross-sectional view of the delivery systemshown in FIG. 7.

FIG. 9 is a side, cross-sectional view of a medical device deliverysystem being advanced through a torturous pathway, according to someembodiments.

FIG. 10 is a side, cross-sectional view of another core assembly,according to some embodiments.

FIG. 11 is a side, cross-sectional view of yet another core assembly,according to some embodiments.

FIG. 12A is a schematic, partial cross-sectional view of the system ofFIG. 1, in which a stent has been initially expanded against a vesselwall and a distal cover of the system is disengaged, according to someembodiments.

FIG. 12B is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the distal cover has migrated to an everted position,according to some embodiments.

FIG. 12C is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the distal cover has migrated to another evertedposition, according to some embodiments.

FIG. 13 is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the stent has been partially expanded against thevessel wall and moved outside of a catheter lumen, according to someembodiments.

FIG. 14 is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the stent has been retracted or resheathed into thecatheter lumen after initial expansion of the stent, according to someembodiments.

FIG. 15 is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the stent and a distal tip assembly of the coreassembly have been retracted or resheathed into the catheter lumen afterinitial expansion of the stent, according to some embodiments.

FIG. 16 is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the stent has been expanded and released from the coreassembly into apposition with the vessel wall, according to someembodiments.

FIG. 17 is a schematic, partial cross-sectional view of the system ofFIG. 1, in which the core assembly has been retracted or received intothe catheter lumen after releasing the stent, according to someembodiments.

FIG. 18A is a schematic, partial cross-sectional view of a stentdelivery system positioned at a treatment site adjacent to a vesselbifurcation.

FIG. 18B is a schematic, partial cross-sectional view of the stentdelivery system and the treatment site shown in FIG. 18A, in which adistal portion of a core member of the stent delivery system has beenrotated to avoid abrading or perforation of a vessel wall, according tosome embodiments.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a full understanding of the subject technology. Itshould be understood that the subject technology may be practicedwithout some of these specific details. In other instances, well-knownstructures and techniques have not been shown in detail so as not toobscure the subject technology.

Described herein are various embodiments of stent delivery systemsexhibiting small cross-sections which are highly flexible and canprovide advantages such as allowing the clinician to recapture,collapse, withdraw, or resheath and reposition a partially expandedstent, avoid vessel abrasions or perforations during placement, placeseveral stents (e.g., “telescoping”) without removing the microcatheter,and/or avoid torsional stress and “whipping” that can occur duringdelivery of the stent. Various other features and advantages ofembodiments are discussed and shown herein.

In some embodiments, a stent delivery system is provided that caninclude a core assembly and an introducer sheath and/or catheter. Thecore assembly can comprise a stent extending over, carried, or supportedby a core member. The core member can comprise a core wire. The coreassembly can be movable within the introducer sheath and/or catheter inorder to deliver the stent to a predetermined treatment site, such as ananeurysm, within the vasculature of a patient. Thus, prior to deliveryof the stent, the catheter can be configured to be introduced andadvanced through the vasculature of the patient. The catheter can bemade from various thermoplastics, e.g., polytetrafluoroethylene (PTFE orTEFLON®), fluorinated ethylene propylene (FEP), high-densitypolyethylene (HDPE), polyether ether ketone (PEEK), etc., which canoptionally be lined on the inner surface of the catheter or an adjacentsurface with a hydrophilic material such as polyvinylpyrrolidone (PVP)or some other plastic coating. Additionally, either surface can becoated with various combinations of different materials, depending uponthe desired results.

The stent can take the form of a vascular occluding device, arevascularization device and/or an embolization device. In someembodiments, the stent can be an expandable stent made of two or morefilaments. The filaments can be formed of known flexible materialsincluding shape memory materials, such as nitinol, platinum andstainless steel. In some embodiments, the filaments can be round orovoid wire. Further, the filaments can be configured such that the stentis self-expanding. In some embodiments, the stent can be fabricated fromplatinum/8% tungsten and 35N LT (cobalt nickel alloy, which is a lowtitanium version of MP35N alloy) alloy wires. In other embodiments, oneor more of the filaments can be formed of a biocompatible metal materialor a biocompatible polymer.

The wire filaments can be braided into a resulting lattice-likestructure. In at least one embodiment, during braiding or winding of thestent, the filaments can be braided using a 1-over-2-under-2 pattern. Inother embodiments, however, other methods of braiding can be followed,without departing from the scope of the disclosure. The stent canexhibit a porosity configured to reduce haemodynamic flow into and/orinduce thrombosis within, for example, an aneurysm, but simultaneouslyallow perfusion to an adjacent branch vessel whose ostium is crossed bya portion of the stent. As will be appreciated, the porosity of thestent can be adjusted by “packing” the stent during deployment, as knownin the art. The ends of the stent can be cut to length and thereforeremain free for radial expansion and contraction. The stent can exhibita high degree of flexibility due to the materials used, the density(i.e., the porosity) of the filaments, and the fact that the ends arenot secured.

Information regarding additional embodiments, features, and otherdetails of the occlusion devices or stents, methods of use, and othercomponents that can optionally be used or implemented in embodiments ofthe occlusion devices or stents described herein, can be found inApplicants' co-pending applications U.S. patent application Ser. No.12/751,997, filed on Mar. 31, 2010; Ser. No. 12/426,560, filed on Apr.20, 2009; Ser. No. 11/136,395, filed May 25, 2005; Ser. No. 11/420,025,filed May 24, 2006; Ser. No. 11/420,027, filed May 24, 2006; Ser. No.12/425,604, filed Apr. 17, 2009; Ser. No. 12/896,707, filed Oct. 1,2010; 61/483,615, filed May 6, 2011; 61/615,183, filed Mar. 23, 2012;61/753,533, titled Methods and Apparatus for Luminal Stenting, filed onJan. 17, 2013; Ser. No. 13/614,349, titled Methods and Apparatus forLuminal Stenting, filed on Sep. 13, 2012; and Ser. No. 13/692,021,titled Methods and Apparatus for Luminal Stenting, filed on Dec. 3,2012; the entireties of each of which are incorporated herein byreference.

For example, in some embodiments, the occluding device or stent may be aself-expanding stent made of two or more round or ovoid wire filaments.The filaments may be formed of flexible materials includingbiocompatible metals or alloys, such as nitinol, platinum,platinum-tungsten, stainless steel, cobalt-chromium, or cobalt-nickel.In some embodiments, the occluding device or stent can be fabricatedfrom a first plurality of filaments of platinum/8% tungsten and a secondplurality of filaments of 35N LT (cobalt nickel alloy, which is a lowtitanium version of MP35N alloy). In other embodiments, one or more ofthe filaments can be formed of a biocompatible metal material or abiocompatible polymer.

The core member can be sufficiently flexible to allow the stent deliverysystem to bend and conform to the curvature of the vasculature as neededfor axial movement of the stent within the vasculature. The core membercan be made of a conventional guidewire material and have a solidcross-section. Alternatively, the core member can be formed from ahypotube. The material used for the core member can be any of the knownguidewire materials including superelastic metals or shape memoryalloys, e.g., nitinol. For example, the core member, along its length orat least at its distal end or tip, can comprise polytetrafluoroethylene(PTFE or TEFLON®). Alternatively, the core member can be formed ofmetals such as stainless steel.

In one or more embodiments, the stent delivery system can exhibit thesame degree of flexion along its entire length. In other embodiments,however, the stent delivery system can have two or more longitudinalsections, each with differing degrees of flexion or stiffness. Thedifferent degrees of flexion for the stent delivery system can becreated using different materials and/or thicknesses within differentlongitudinal sections of the core member. In another embodiment, theflexion of the core member can be controlled by spaced cuts (not shown)formed within the core member. These cuts can be longitudinally and/orcircumferentially spaced from each other.

In some embodiments, the core assembly can secure, grasp, or engage in aproximal end of the stent to facilitate recapture, retraction,withdrawal, or resheathing of the stent into the catheter lumen. Thecore assembly can optionally comprise a constraining member orcontainment sheath. Further, the core member of the core assembly canoptionally comprise at least one engagement component, protrudingmember, stop member or restraint, sleeve, bumper, or other variablediameter portion providing a radially-extending dimension, disposedalong the length of the core member that can cooperate with theconstraining member or containment sheath to secure, grasp, or engagethe stent in a press, friction, or interference fit. Although someembodiments may refer to one or another type of engagement component orprotruding member, various structures can be used in accordance withvarious implementations of these embodiments. Accordingly, in someembodiments, the constraining member and the engagement component cancooperate to form a gripping mechanism that engages a proximal or firstportion of the stent. The gripping mechanism can secure or engage thefirst portion of the stent in a collapsed or expanded state.

For example, the containment sheath can be movable relative to the coremember and configured to receive a proximal or first end of the stent.When assembled, the stent can extend over the core member with aproximal or first portion of the stent extending over a variablediameter portion of the core member and the proximal end of the stentreceived axially within a distal end of the containment sheath. Thedistal end of the containment sheath and the variable diameter portionof the core member can be axially spaced or offset from each other. Thespacing of the distal end of the containment sheath and the variablediameter portion of the core member can be configured to create a press,friction or interference fit with the stent extending therebetween inorder to secure, grasp, retain, or engage the first portion of thestent. Accordingly, the variable diameter portion or engagementcomponent can cooperate with the containment sheath or constrainingmember to inhibit expansion of the proximal or first portion of thestent.

In some embodiments, the first portion of the stent can be secured,grasped, retained, maintained, or engaged in a collapsed or unexpandedstate. Further, in some embodiments, the first portion of the stent canbe secured or engaged in a manner that induces a change in diameter inthe first portion of the stent. For example, the first portion of thestent can extend over or be seated on the variable diameter portion ofthe core member while a section of the first portion of the stent isdisposed axially within the distal end of the containment sheath, whichsection is urged to a smaller diameter size than the diameter size ofthe first portion extending over or seated on the variable diameterportion of the core member. Furthermore, in some embodiments, the distalend of the containment sheath can abut a diameter-changing portion ofthe stent to thereby create a press, friction, or interference fit.

In some embodiments, the variable diameter portion of the core membercan comprise one or more steps and/or axially extending protrusions. Thevariable diameter portion can be formed as an integrated structure ofthe core member (e.g., the core member and the variable diameter portioncan be formed from a single, continuous piece of material). However, thevariable diameter portion can be a separate structure that is placedonto, coupled, and/or attached to the core member. Further, in someembodiments, the variable diameter portion can be fixed relative to thecore member. In other embodiments, the variable diameter portion can berotationally and/or longitudinally movable relative to the core member.

For example, the variable diameter portion can comprise a cylindricalstructure or support member that is configured to rotate about the coremember, but can be fixed in a longitudinal position (or have a limitedrange of longitudinal movement) relative to the core member.Accordingly, in some embodiments, the variable diameter portion canfacilitate rotation of the stent. Typically, during delivery of thestent to the treatment site, passing through tortuous vessels can inducea torsional stress in the delivery system and/or stent. However, in someembodiments, a rotatable (preferably cylindrical) variable diameterportion can support the stent and allow the stent to rotate about thecore member, thereby alleviating torsional stresses during delivery.Such a rotatable variable diameter portion can thus reduce or eliminatethe tendency of the stent to “whip” when released or expanded.“Whipping” is the rapid, rotational unwinding that sometimes occurs whenthe stent is released, due to the release of torsional forces that havebeen exerted on the stent during delivery. Further, the rotatablevariable diameter portion can also allow the core assembly to exhibitgreater flexibility during delivery of the stent to the treatment site.

Further, the securement or engagement of the first portion of the stentcan allow a clinician to exert a distal pushing force on the stent todistally advance the stent relative to the catheter, as well as to exerta proximal pulling force on the stent to proximally withdraw or retractthe stent into the catheter, even after the entire stent has been moveddistally beyond a distal end of the catheter and partially expanded intoapposition with a vessel wall.

Indeed, after navigating the core assembly along the length of thecatheter to the treatment site within the patient, the stent can bedeployed from the catheter in a variety of ways. In one embodiment, thecatheter can be retracted while maintaining the position of the coremember to expose the distal end of the core member and the distal end ofthe stent. While this is being done, the stent can be engaged in acollapsed state at least at the proximal end or portion thereof. In someembodiments, the stent can be engaged at both the proximal and distalends or portions thereof while the catheter is being retracted.

For example, the catheter can be proximally withdrawn relative to thecore assembly, thereby exposing a distal tip assembly of the coreassembly. The distal portion or assembly of the core assembly cancomprise a distal tip structure and/or a flexible distal cover.

The distal tip structure can comprise at least one member or componentthat can be carried by the core member. In some embodiments, the atleast one member can be oriented generally transverse or parallel to thecore member. For example, the tip structure can comprise a coil(s), acircumferentially-extending band(s) of material, a clamp(s), and/orother structures that can pass smoothly within a vessel at the distalportion of the core member. Further, the at least one member cancomprise at least one segment of the coil or other structure.

In some embodiments, the distal cover can at least partially cover orsurround a distal end of the stent extending over an intermediateportion of the core assembly in a first, wrapping, delivery, orpre-expansion position. For example, in this position, the core assemblycan be positioned axially within the lumen of the catheter such that thedistal end of the stent is positioned axially adjacent to the distal endof the catheter with at least a portion of the distal cover extending ina space within the catheter lumen radially between the distal end of thecatheter and at least one of the stent or the intermediate portion ofthe core assembly. The distal cover can extend proximally from thedistal portion or assembly and the space between the distal portion andthe catheter. Further, in some embodiments, at least a portion of thedistal cover can be positioned outside of a space radially between thedistal tip structure of the core assembly and the catheter. Accordingly,in some embodiments, the distal cover can comprise one or more strips ofa flexible and/or lubricious material that can be positioned radially inbetween portions of the distal end of the stent and the inner surface ofthe catheter to reduce sliding friction between the core assembly andthe catheter.

However, as the distal end of the stent is unsheathed or moved beyondthe distal end of the catheter lumen, the distal end of the stent canbegin expanding and thereby urge the distal cover from the first,wrapping, delivery, or pre-expansion position or configuration to asecond, unfurled, expanded, resheathing, or everted position orconfiguration. As the distal cover moves to the everted position orconfiguration, the distal end of the stent can be expanded intoapposition with the vessel wall. If the stent is “landed” at the correctposition within the vessel, the remainder of the stent can beunsheathed, expanded, and released into the target vessel.

However, in accordance with some embodiments, after the stent has beenpartially expanded and even if the stent has been fully unsheathed ormoved beyond a distal end of the catheter, the stent delivery system canallow the clinician to recapture, collapse, withdraw, or resheath thestent into the catheter and later deploy, expand or unsheath the stentagain from the catheter. As noted above, some embodiments allow thestent to be proximally secured, grasped, or engaged by the core assemblyin order to both exert a distal pushing force on the stent and to exerta proximal pulling force on the stent. Thus, even when the stent hasbeen fully unsheathed or moved beyond a distal end of the catheter, aproximal end of the stent can remain secured, grasped, or engaged withthe core assembly to allow the stent to be retracted or withdrawnproximally into the catheter until the entire length of the stent hasbeen resheathed into the catheter. In accordance with some embodiments,the distal cover can be retracted or withdrawn into the catheter in itssecond, unfurled, expanded, resheathing, or everted position orconfiguration.

For example, while the stent is being retracted or withdrawn back intothe catheter, the distal cover can be positioned outside of the spaceradially between the catheter and at least one of the stent or theintermediate portion to provide a clearance therebetween and facilitateresheathing for retraction of the stent and core assembly into thecatheter. Further, in some embodiments, the distal cover can bepositioned in the space radially between the catheter and the distal tipstructure of the core assembly. Thereafter, the catheter and/or coreassembly can be repositioned axially within the vasculature at a desiredlocation and the stent can be unsheathed, expanded, landed, and releasedinto the vasculature if the placement location is proper.

Therefore, in accordance with some embodiments, the distal cover canfacilitate resheathing of the core assembly. The resheathing of the coreassembly can be done with or without the stent engaged or secured withthe core assembly.

In some embodiments, the distal cover can also facilitate the retractionand withdrawal of the core assembly after the stent has been releasedinto the vasculature. As noted, the distal cover can be withdrawn intothe catheter in its second, unfurled, expanded, resheathing, or evertedposition or configuration. Whether or not the stent has been releasedinto the vasculature, the entire core assembly can be withdrawnproximally into the catheter and proximally removed from the catheter.Thus, if the stent has been released into the vasculature, the coreassembly can be removed from the catheter and a second core assembly canbe introduced into the catheter in order to deploy a second stent at thetreatment site. Such embodiments can provide significant advantages to aclinician including, for example, that the catheter need not bewithdrawn and removed from the vasculature in order to deploy a first orsubsequent stent to the treatment site. Accordingly then, thevasculature or need not undergo additional stress and the operation canbe performed with greater speed and efficiency.

The stent delivery system can also optionally include a steerable tipmechanism or steerable tip assembly. The steerable tip mechanism canallow a clinician to avoid abrading or perforating the vessel wallduring the procedure. In some embodiments, the steerable tip mechanismcan comprise a steerable wire having a curvilinear distal end. Forexample, a core member of the core assembly can be configured to besteerable by being rotatable relative to an engagement component (ifpresent) and the stent, the catheter, and/or other components of thestent delivery system. The core member can comprise a core wire.Further, the core wire can comprise a curved or arcuate distal sectionthat can be rotated or reoriented, for example, by importing rotationvia the core wire core member, to point the core wire in a desireddirection by rotating the core wire. Accordingly, in some embodiments,the rotation of the core member relative to the stent can allow theclinician to avoid dislodging the stent from the vessel wall afterinitial expansion of the stent and also avoid abrasion or perforation ofthe blood vessel.

For example, in some embodiments, the stent can extend over anengagement component of the core member and be secured or restricted formovement relative to the engagement component and a constraining member.The engagement component can be rotatably coupled to or supported on thecore member such that the core member is rotatable relative to thestent, the engagement component, and the constraining member.Accordingly, rotation of the core member can allow a clinician to adjustthe position or orientation of a terminal or distal portion of the coremember. Further, in some embodiments, the distal portion of the coremember can be formed in an arcuate or curved configuration to enable thecore member to conform to tortuous vessel geometries. For example, thedistal portion of the core member can comprise a curled, curved orarcuate tip that extends distally from the core member and is orientedtransverse to or bends away from a central axis of the catheter lumen.

Therefore, if the treatment site is adjacent to a tortuous vessellocation (e.g., a sharp turn in the vessel) or a bifurcation, forexample, the clinician can select or control the direction in which thecore member extends in order to avoid abrasions or perforations of thevessel during expansion and delivery of the stent at the treatment site.

For example, prior to or during unsheathing of the stent at thetreatment site, the clinician can observe the position of the distal tipassembly of the core member relative to surrounding vasculature. As thestent expands during the deployment process, it may generallyforeshorten, which can require or cause the core assembly including thedistal tip assembly to move distally to accommodate the shortening ofthe stent. This distal movement of the tip assembly to accommodate theshortening of the stent. This distal movement of the tip assembly canpresent an abrasion or perforation hazard, or a risk that the distal tipmay engage the vessel wall in a manner that can create an abrasion orperforation in the vessel. If the clinician can identify an abrasion orperforation hazard, the clinician can evaluate whether reorienting thetip would allow it to move distally without producing an abrasion orperforation. The clinician can use a proximal actuator of the stentdelivery system to rotate the core member, thereby rotating the distaltip of the core member. In some embodiments, the distal tip can have acurvilinear or arcuate configuration. In some embodiments, the arcuateor curved part of the tip can be radiopaque to enable the physician toobserve via fluoroscopy or other imaging the orientation of the tiprelative to the surrounding vasculature, and determine whether the tipshould be rotated or reoriented into a position wherein the furtherdistal advance of the core assembly is less likely to injure thevasculature. Such a position could be one wherein the tip points towarda lower-risk path (e.g., at a bifurcation, the gentler rather than thesharper of the turns provided at the bifurcation, or the larger ratherthan the smaller vessel). Thus, rotation of the distal tip can reorientthe direction of the core member to avoid a bifurcation apex, a sharpturn in the vessel, or other structures of the vasculature which mayrepresent an abrasion or perforation hazard. Thereafter, if the coremember is distally advanced axially within the vasculature, a properlyoriented distal tip can follow the path of the vasculature withoutabrading, perforating, or otherwise damaging the vessel wall.

Additionally, in some embodiments, the core assembly of the stentdelivery system can be configured to comprise one or more rotatableengagement components mounted on the core member or core wire. Theengagement component can be positioned axially adjacent to a distal endof a constraining member extending over the core member. In someembodiments, the engagement component can have a cross-sectional outerprofile that is sized about equal to or greater than the cross-sectionalinner profile of the catheter. For example, the engagement component canhave a cross-sectional outer profile that is sized greater than theinner profile of the catheter.

Further, in some embodiments, the distal tip assembly or structure,e.g., including the distal cover, can be configured to rotate about thecore member. For example, an end of the distal cover can be rotatablycoupled with respect to the core member. Thus, the stent can beconfigured to rotate about the core member at least in part by virtue ofthe rotatable coupling of the distal cover.

As noted similarly above in other embodiments, a stent can extend overthe engagement component and be engaged or secured between theengagement component and the constraining member. In some embodiments,the engagement component can extend continuously around the core member.However, the engagement component can also extend around only a portionof the core member. The stent can have a variable diameter from a firstportion to a second portion thereof as the stent is engaged in africtional and/or interference fit. The rotatable engagement componentcan allow the core assembly to exhibit torsional flexibility which canreduce the pushing force required to move the core assembly through thecatheter the treatment site.

FIGS. 1-6 depict embodiments of a stent delivery system 100 which may beused to deliver and/or deploy a stent 200 into a hollow anatomicalstructure such as a blood vessel 102. The stent 200 can comprise aproximal end 202 and a distal end 204. The stent 200 can comprise abraided stent or other form of stent such as a laser-cut stent, roll-upstent etc. The stent 200 can optionally be configured to act as a “flowdiverter” device for treatment of aneurysms, such as those found inblood vessels including arteries in the brain or within the cranium, orin other locations in the body such as peripheral arteries. The stent200 can optionally be similar to any of the versions or sizes of thePIPELINE™ Embolization Device marketed by Covidien of Mansfield, Mass.USA. The stent 200 can further alternatively comprise any suitabletubular medical device and/or other features, as described herein.

As shown in FIG. 1, the depicted stent delivery system 100 can comprisean elongate tube or catheter 110 which slidably receives a core assembly140 configured to carry the stent 200 through the catheter 110. FIG. 2illustrates the core assembly 140 without depicting the catheter 110 forclarity. The depicted catheter 110, 710 (see FIGS. 1, 5, 7-8, and12A-13) has a proximal end 112 and an opposing distal end 114, aninternal lumen 116 extending from the proximal end 112 to the distal end114, and an inner surface 118 facing the lumen 116. At the distal end114, the catheter 110 has a distal opening 120 through which the coreassembly 140 may be advanced beyond the distal end 114 in order toexpand the stent 200 within the blood vessel 102. The proximal end 112may include a catheter hub 122.

The catheter 110 can optionally comprise a microcatheter. For example,the catheter 110 can optionally comprise any of the various lengths ofthe MARKSMAN™ catheter available from Covidien of Mansfield, Mass. USA.The catheter 110 can optionally comprise a microcatheter having an innerdiameter of about 0.030 inches or less, and/or an outer diameter of 3French or less near the distal end 114. Instead of or in addition tothese specifications, the catheter 110 can comprise a microcatheterwhich is configured to percutaneously access the internal carotidartery, or a location within the neurovasculature distal of the internalcarotid artery, with its distal opening 120.

Information regarding additional embodiments of the catheter 110, andadditional details and components that can optionally be used orimplemented in the embodiments of the catheter described herein, can befound in U.S. Patent Application Publication No. US 2011/0238041 A1,published on Sep. 29, 2011, titled Variable Flexibility Catheter. Theentirety of the aforementioned publication is hereby incorporated byreference herein and made a part of this specification.

The core assembly 140 can comprise a core member 160 configured toextend generally longitudinally through the lumen 116 of the catheter110. The catheter 110 can define a generally longitudinal axis extendingbetween a proximal end and a distal end thereof. As discussed herein,the distal end of the catheter 110 can be positioned at a treatment sitewithin a patient. The core member 160 can comprise an intermediateportion 614 which is the portion of the core member onto or over whichthe stent 200 is positioned or extends when the core assembly 140 is inthe pre-deployment configuration as shown in FIGS. 1-5B, 13A and 13B.The stent 200 can be fitted onto or extend over the intermediate portionof the core member 160. The core member 160 can comprise a core wire.The core member 160 can have a proximal end or section 162 and aterminal or distal end 164. In some embodiments, the distal end 164and/or other portions of the core member 160 can be tapered such thatthe core member 164 becomes thinner as it extends distally.

The core member 160 can be coupled with, terminate at, or end in adistal tip. In some embodiments, the core member 160 can comprise aproximal section and a distal section. The distal section of the coremember 160 can be a distal tapering section, as illustrated. The distaltapering section can have a gradual taper that continues to the distaltip of the core member 160.

The distal tip of the core member 160 can comprise a distal portion orassembly 180. In some embodiments, the distal tip assembly 180 cancomprise a distal tip structure 182 and/or a distal cover 400 orstent-engaging portion. The distal tip structure 182 can comprise atleast one member or component that can be carried by the core member160. In some embodiments, the at least one member can be orientedgenerally transverse or parallel to the core member 160. For example,the tip structure 182 can comprise a coil(s), acircumferentially-extending band(s) of material, a clamp(s), and/orother structures that can pass smoothly within a vessel. Further, the atleast one member can comprise at least one segment of a coil or otherstructure.

In the illustrated embodiment, the core wire can optionally beconfigured to extend through the distal tip assembly 180 and terminateat the distal end 164. In some embodiments, the core member 160 can beconfigured to transmit torque and axial/longitudinal force from theproximal end 162 of the core member 160 to the distal end 164, where thedistal tip assembly 180 is disposed.

The distal end 164 of the core member 160 can be a flattened section ofthe core member 160. The distal end 164 can be flattened from a tapereddiameter of the core member 160 to a generally rectangular cross-sectionhaving a thickness sized less than the diameter of the adjacent portionof the core member. For example, the distal end 164 can have a thicknessof between about 0.0005 inches to about 0.003 inches. The distal end 164can thus be flattened from a distal portion of the core member 160having a diameter of between about 0.003 inches to about 0.005 inches.In some embodiments, the distal end 164 can be a flat portion having athickness of about 0.001 inches. Additionally, the length of the flatportion of the distal end 164 can be between about 8 mm and about 15 mm.In some embodiments, the length of the flat portion of the distal end164 can be between about 10 mm and about 12 mm. Whether in the form ofthe flattened wire described above, or of a distally extending tip coil,or other configuration, the distal end 164 can optionally be coveredwith or include radiopaque material, such as a radiopaque polymer. Onesuitable radiopaque polymer is a thermoplastic polyurethane (e.g.,PELLETHANE™ 80A or TECOFLEX™) doped with a radiopacifier such astungsten or barium sulfate.

As illustrated in FIGS. 1-2, some embodiments of the core member 160 canbe configured with an arcuate or curved distal end 164. The distal end164 extends distally from the core member 160 and can be orientedtransverse to or bend away from a central axis of the catheter lumen116. The distal end 164 can be curved or bent to form an angle ofapproximately 45 degrees with the longitudinal axis of the core member160. The distal end 164 can be heat-set or otherwise processed to retainthe arcuate/curved/angled configuration. As discussed further herein,the core member 160 can be twisted or torqued to rotate the arcuate orcurved distal end 164 thereof in order to advantageously allow aclinician to carefully navigate and steer the distal tip assembly 180and core member 160 through tortuous vessel geometry, thereby avoidingabrasion or perforation of a vessel wall.

The distal tip assembly 180 may be coupled axially adjacent to thedistal end 164 of the core member 160. Moreover, the core member 160 mayextend into and form a core of the distal tip assembly 180, or otherwisebe connected to the distal tip assembly 180.

In some embodiments, the distal tip assembly 180 can be rotatablycoupled to the distal end 164 of the core member 160. As discussedfurther herein, a rotatable coupling between the distal end 164 of thecore member 160 and the distal tip assembly 180 can allow the coremember 160 to rotate independently relative to the distal tip assembly180 (and possibly other components of the core assembly 140). Suchrelative rotation can advantageously impart greater flexibility to thecore assembly 140 as it is passed through the catheter 110 to thetreatment site. Further, in embodiments in which the distal end 164 ofthe core member 160 extends distally beyond the distal tip assembly 180,such relative rotation can also advantageously allow the distal end 164to be rotated independently of the distal tip assembly 180, which mayreduce any torsional stress on the stent 200, the core assembly 140,and/or the surrounding vasculature.

However, in other embodiments, the distal tip assembly 180 can berigidly or fixedly coupled to the distal end 164 of the core member 160such that the distal tip assembly 180 and the core member 160 rotate asa single unit. For example, the core member 160 can be operativelycoupled with the distal tip assembly 180 such that the distal tipassembly 180 is usable to radially direct or steer the core member 160within the catheter 110 and/or a blood vessel by twisting or torquingthe core member 160.

The distal tip structure 182 can be configured to comprise an atraumaticdistal end face formed by a rounded solder bead, especially inembodiments in which the distal end 164 of the core member 160 does notextend distally beyond the distal tip assembly 180. Further, the distaltip structure 182 can have other atraumatic shapes designed to avoidinjury to the vessel into which it may be introduced.

The core member 160 can be sufficiently flexible to allow flexure andbend as it traverses tortuous blood vessels. In some embodiments, thecore member 160 can be tapered along at least part of its length orcontain multiple tapering or stepped sections of different diameters orprofiles, and become narrower and more flexible as it extends distally.

The core assembly 140 may also optionally include a proximal retainingmember 220 located proximal of the stent 200. The proximal retainingmember 220 can comprise one or more materials. For example, in someembodiments, the proximal retaining member 220 may include a marker band222 fixed to the core member 160 via a solder bead 224 or other suitableconnection. The marker band 222 may be a generally cylindrical structuremade of platinum or other radiopaque material. In at least oneembodiment, the proximal retaining member 220 may be arranged in thecore assembly 140 such that there is a small gap, e.g., from about 0.0mm to about 0.5 mm, axially between the band 222 of the retaining member220 and the proximal end 202 of the stent 200.

In embodiments where the marker band 222 of the proximal retainingmember 220 is made of platinum or another radiopaque material/substancevisible through fluoroscopy, CAT scan, X-Ray, MRI, ultrasound technologyor other imaging, a user may be able to determine the location and trackthe progress of the proximal end 202 of the stent 200 within thecatheter 110 or blood vessel 102 by determining the location of theproximal retaining member 220.

Instead of, or in addition to, the depicted components of the proximalretaining member 220, the retaining member 220 may include a marker coil(not shown) or a coil or other sleeve (not shown) having alongitudinally oriented, distally open lumen that at least partiallyreceives and surrounds the proximal end 202 and/or other proximalportion of the stent 200. Further, the proximal retaining member 220 canalso comprise a biasing member, such as a coil spring wound around thecore member 160, which can be configured to bias the stent 200 in thedistal direction.

Referring now to FIG. 3A, some embodiments of the system 100 can alsocomprise a stent holding assembly 300 configured to releasably engage afirst portion 206 of the stent 200. The stent holding assembly 300 canenable a clinician to secure, grasp, or engage the first portion 206 ofthe stent 200 in a manner that allows the stent to be controlled,positioned, and released at a precise, desired position within thevessel. In some embodiments, the stent holding assembly 300 can enable aclinician to push the stent distally, pull the stent proximally,unsheath or move the stent distally beyond the distal end of thecatheter, and/or recapture, collapse, withdraw, or resheath the stentinto the catheter after the stent has been partially expanded within thevessel.

Further, in accordance with some embodiments, the stent holding assembly300 can be configured to accomplish such superior control using only thesecurement, grasping, or engagement between the stent holding assembly300 and the first portion 206 of the stent 200. Thus, a distal portion210 of the stent need not undergo or directly receive the pushing orpulling forces exerted by the clinician. Instead, the distal portion 210of the stent can be guided by the forces exerted on the first portion ofthe stent and generally expand freely when moved outside of thecatheter. As such, the clinician can carefully control the axialposition of the distal portion of the stent in order to properly landthe stent within the vessel and should the stent need to berepositioned, the clinician can recapture, collapse, withdraw, orresheath the stent into the catheter and attempt to land the stent againwithin the vessel at the desired position.

The stent holding assembly can comprise one or more components thatcooperate to secure, grasp, or engage a portion of the stent 200. Insome embodiments, a component attached to, coupled to, carried by, orformed on the core member 160 can cooperate with other structures of thesystem 100 in order to provide such superior stent control.

For example, as seen in FIGS. 2-3A, the core assembly 140 can alsocomprise a constraining member or outer grip member 320. Theconstraining member 320 can have a proximal end 322 and a distal end324. The constraining member 320 can comprise an elongate sheath havinga central lumen extending between the proximal end 322 and the distalend 324. The central lumen can be configured to receive the core member160 therethrough.

In some embodiments, the constraining member can be a simple tube orsheath. For example, the constraining member can have an inner diameterof between about 0.015 inches and about 0.023 inches. The inner diametercan also be between about 0.017 inches and about 0.021 inches. In someembodiments, the inner diameter can be about 0.017 inches or about 0.021inches. Further, an outer diameter of the constraining member can bebetween about 0.018 inches and about 0.028 inches. The outer diametercan also be between about 0.020 inches and about 0.026 inches. In someembodiments, the outer diameter can be about 0.020 inches or about 0.025inches. The axial length of the constraining member can also be betweenabout 150 cm and about 200 cm. Further, the constraining member can beformed from a flexible material. For example, the constraining membercan be formed from material such as PTFE, polyimide, or other suchpolymers.

However, the constraining member can also be configured as a structuralalternative to a simple tube or sheath. Such structures can include adistal end portion that is “fully” tubular coupled to a proximal portionthat is made up of one or more longitudinal struts or wires, or thatcomprises a slotted or spiral-cut tube. In any of the disclosedconstraining members, the distal end portion may comprise a coil (e.g.,a metallic coil) or other form of proximally retractable sleeve suitablysized for use in the core assembly 140.

Further, the core assembly 140 can also comprise at least one engagementcomponent, protruding member, stop member or restraint, sleeve, bumper,or variable dimension portion providing a radially-extending dimension,disposed along the core member. The engagement component can comprise aprotrusion or a recess disposed along the core member 160. For example,the engagement component can comprise an protruding member, stop memberor restraint, sleeve, bumper, or variable dimension portion 340. Theengagement component 340 can be a radially extending component. Theengagement component 340 can be disposed along the core member 160between the distal section 164 and the proximal section 162 thereof. Forexample, the engagement component 340 can be disposed axially betweenthe proximal section 162 and the distal section of the core member 160.In accordance with some embodiments, the stent holding assembly 300 canbe configured such that the constraining member 320 and the engagementcomponent 340 cooperate to secure, engage, or grip the proximal end 202and/or first portion 206 of the stent 200. Further, the constrainingmember 320 can be longitudinally displaceable relative to the coremember 160 and/or the engagement component 340 to release the firstportion of the stent and allow it to expand within the vessel. Thus,during axial advancement or withdrawal of the stent 200 within the lumen116 of the catheter 110 or expansion of the stent 200 within the vessel,the first portion 206 of the stent 200 can be controlled by the stentholding assembly 300.

In some embodiments, the stent holding assembly 300 can be configuredsuch that one or more components thereof define a capture area in whichat least a portion of the first portion of the stent can be secured,engaged, or grasped. The capture area can extend around at least aportion of the circumference of the core member 160. Accordingly, atleast a portion of the circumference of the first portion of the stentcan be secured, engaged, or grasped in the capture area.

As shown in FIG. 3A, the depicted embodiment illustrates that theconstraining member 320 can comprise a tube or sheath that receives aportion of the core member 160 in a lumen of the constraining member320. The distal end 324 of the constraining member 320 can be spacedapart from the core member 160 to define a capture area 350therebetween. The capture area 350 in the illustrated embodiment can beformed as a generally cylindrically shaped gap configured to receive atleast the proximal end 202 of the stent 200 therewithin. Accordingly,the distal end 324 of the constraining member 320 can circumferentiallyat least partially cover or surround at least the proximal end 202 ofthe stent 200 when the proximal end 202 is received axially within thecapture area 350.

In some embodiments, a distal portion of the constraining member can befitted over or extend over the proximal end of the stent. As shown inFIGS. 1-3A, proximal end 202 of the stent 200 can be positioned in thelumen of the constraining member 320; preferably the proximal endportion of the stent 200 is slightly radially compressed and liesradially adjacent to the inner wall of the constraining member 320. Theengagement component 340 can hold the first portion of the stent 200 inthe constraining member 320. Where the engagement component 340 islocated distal of the distal end of the constraining member 320, thiscan be accomplished in whole or in part by engaging, securing, orgripping the stent 200 between the engagement component 340 and the rimof the distal opening of the constraining member 320. In suchembodiments, the stent 200 can be engaged, secured, or gripped in agenerally axial direction. Where the engagement component 340 ispositioned partly or wholly within the lumen of the constraining member320, this can be accomplished in whole or in part by gripping the stent200 between the outer surface of the engagement component 340 and theinner surface of the constraining member 320. In such embodiments, thestent 200 can be engaged, secured, or gripped in a generally radialdirection. Further, some embodiments can be provided in which the stent200 can be engaged, secured, or gripped in a direction transverse to theradial and axial directions.

In certain embodiments, the outer surface of the engagement component340 can be tapered such that its outer diameter increases in a distaldirection, and the inner surface of the constraining member 320 may betapered to match the taper of the engagement component 340. In thoseembodiments, the stent 200 may be gripped between the outer surface ofthe engagement component 340 and the inner surface of the constrainingmember 320, and/or between the engagement component 340 and the rim ofthe distal opening of the constraining member 320.

With reference to FIGS. 1-4B and 7-10, preferably only a relativelysmall portion (e.g., significantly less than half the length, or lessthan 25% of the length, or less than 10% of the length) of the stent 200is positioned axially within the constraining member 320. In thedelivery or in-catheter configuration shown in FIG. 1, the balance ofthe stent 200 extends distally and somewhat radially outward of thedistal end 324 of the constraining member 320, preferably lying radiallyadjacent the inner surface 118 of the catheter 110 except where thedistal portion 210 of the stent extends into a distal cover or distalstent covering 400 (discussed further herein). For example, the axiallength of the constraining member that extends over the stent can bebetween about 4 mm and 15 mm. The axial length of the constrainingmember that extends over the stent can also be between about 6 mm and 10mm. Further, in some embodiments, the axial length of the constrainingmember that extends over the stent can be about 8 mm.

Further, in the embodiment of FIG. 3A, the retaining member 220 is shownin dashed lines to illustrate that this component can optionally beincluded in some embodiments of the stent holding assembly 300. Thesecurement, gripping, or engagement of the first portion 206 of thestent 200 can be accomplished with or without the use of the retainingmember 220. However, in some embodiments, the retaining member 220 canprovide a proximal limit to stent migration and tend to ensure that thestent 200 does not migrate proximally as the constraining member 320 ismoved proximally relative to the engagement component 340 when the stent200 is being released. The retaining member 220 can be formed integrallywith the core member 160, such as being formed from a single, continuouspiece of material. However, the retaining member 220 can also be formedseparately from and later coupled to the core member 160. In someembodiments, the retaining member 220 can be fixed relative to the coremember 160. However, the retaining member 220 can also be free to rotateand/or slide longitudinally along the core member 160.

In accordance with some embodiments, the engagement component 340 canextend in a radial direction about at least a portion of thecircumference of the core member. The engagement component can have anouter surface that extends radially beyond or is spaced radially apartfrom an outer surface of the core member. The engagement component canbe generally cylindrically shaped, oval shaped, or annularly shaped. Theengagement component can be an annular ring, a cylindrical sleeve, orother such structure. However, the engagement component can also haveone or more radially extending protuberances that do not extend aboutthe entire circumference of the core member. The engagement componentcan also be configured to extend along at least a portion of the axiallength of the intermediate portion of the core member.

The engagement component can be formed from a material that can beshrink-fitted onto the core member. The engagement component can also beconfigured to comprise one or more materials. For example, in someembodiments, the engagement component can formed from a material having30% BaSO4. The engagement component can define an axial length ofbetween about 1 mm and about 5 mm. In some embodiments, the engagementcomponent can define an axial length of between about 2 mm and about 4mm. Further, in some embodiments, the engagement component can define anaxial length of about 2 mm. The engagement component can define an innerdiameter of between about 0.005 inches and about 0.015 inches. The innerdiameter can also be between about 0.009 inches and about 0.013 inches.In some embodiments, the inner diameter can be about 0.006 inches, about0.007 inches, or about 0.011 inches. Furthermore, in some embodiments,the engagement component can define an outer diameter of between about0.013 inches and about 0.030 inches. The outer diameter can also bebetween about 0.019 inches and about 0.025 inches. In some embodiments,the outer diameter can be about 0.014 inches or about 0.020 inches.

The engagement component can be formed integrally with the core memberas a single, continuous piece of material. For example, the engagementcomponent can be an enlarged portion of the core member having adiameter or profile that is sized greater than a diameter or profile ofthe axially adjacent portions of the core member. However, theengagement component can also be formed separately from the core memberand coupled thereto. For example, in some embodiments discussed furtherherein, the engagement component can be rotatably coupled to the coremember. Alternatively, the engagement component can also be fixedlycoupled to the core member.

Further, one or more engagement components can be used in someembodiments. For example, as shown in FIG. 6, the core assembly 640 isillustrated with a first engagement component 644 and a secondengagement component 646 positioned along a core member 660. The firstand second engagement components 644, 646 can be configured or operatein accordance with the configurations and functions discussed hereinwith respect to any of the embodiments of the engagement components.Further, the first and second engagement components 644, 646 can beconfigured to slide relative to each other or otherwise cooperate tosupport the stent on the core assembly 640.

With reference again to FIG. 3A, the engagement component 340 is shownas a radially prominent component that is integrally formed with thecore member 160 from a continuous piece of material. The engagementcomponent 340 is a generally cylindrically shaped component having aproximal section 342. The proximal section 342 can comprise a proximalwall extending in a radial direction upwardly from the core member 160,an outer circumferential surface extending generally parallel relativeto a longitudinal axis of the core member 160, and/or an edge formedbetween the proximal wall and the outer circumferential surface. Theedge can be rounded or be formed having a generally perpendicularorientation.

The engagement component 340 can alternatively comprise a component thatis separate from the core member 160 (see, e.g., FIG. 1). Such anengagement component can comprise, for example, a tube of polymer orother suitable material that is attached to the core member 160 viaadhesives, heat shrinking, or any other suitable technique. In oneembodiment, the engagement component 340 comprises a polymeric tubewhich surrounds the core member 160, which passes through a lumen of thetube. One or more coils of metallic wire (such as platinum orplatinum-alloy wire, not shown) can be wrapped around and welded to thecore member 160, and thereby interposed between the core member and thepolymeric tube to serve as a mechanical interlock therebetween.Preferably, the tube is heat shrink material such as PET that isheat-shrunk onto the outer surface of the coil(s), so that the shrunkentube adheres closely to the coil(s) and becomes securely attached to thecore member 160. An engagement component 340 that can rotate about,and/or move longitudinally along, the core member 160 can be constructedin a somewhat similar manner. In this case, the underlying coil(s) canhave a luminal inside diameter that is slightly larger than the outsidediameter of the core member 160. The desired coil luminal insidediameter can be set by winding the coil(s) on an appropriately sizedmandrel. The polymeric tube is then heat-shrunk onto the coil(s) (orotherwise joined thereto) to form the outer portion of the engagementcomponent 340. The resulting engagement component 340 is then slid overthe core member 160 to its desired position thereon, where theengagement component can rotate and/or translate with respect to thecore member. Stop member(s) or restraint(s) can be formed on the coremember 160 proximal and/or distal of the rotatable/translatableengagement component 340, to set boundaries for any longitudinalmovement of the engagement component and allow it to rotate. Suchrestraint(s) can be formed in the manner described above for the fixedengagement component, with an underlying coil welded to the core memberand an overlying shrink tube, but at a somewhat smaller outside diameterthan the engagement component.

For example, FIGS. 5C and 7-11 illustrate embodiments of a system havingat least one rotatable component coupled to the core member betweenrestraints that have a tapered configuration. FIG. 5C illustrates adistal cover that is rotatably attached to a core member and positionedin a gap between restraints. FIGS. 10-11 illustrate additionalembodiments in which at least one engagement component is rotatablycoupled to the core member and positioned within a gap between adjacentrestraints.

As illustrated in FIG. 3A, the first portion 206 of the stent 200 canextend over the engagement component 340 and the proximal end 202 of thestent can extend into the capture area 350 formed radially between theconstraining member 320 and the core member 160. In this embodiment,these components cooperate to form the stent holding assembly 300, whichcan secure, engage, or grip the proximal end 202 and/or first portion206 of the stent 200. Thus, during axial advancement or withdrawal ofthe stent 200 within the lumen 116 of the catheter 110 or duringexpansion of the stent 200 within the vessel, the first portion 206 ofthe stent 200 can be controlled by the stent holding assembly 300.

In particular, the engagement component 340 and the constraining member320 can cooperate to engage, secure, or grasp the stent 200 in a pressfit, an interference fit, or a frictional fit, as illustrated in FIGS.3A-4B. The presence of the engagement component 340 can create a slightincrease in the diameter of the stent 200 axially adjacent to the distalend 324 of the constraining member 320. Thus, the diameter of theproximal end 202 of the stent 200 within the capture area 350 can becomesmaller than the diameter of the stent 200 extending over the engagementcomponent 340. Instead of or in addition to these conditions, the stent200 can be in frictional contact with a distal inner surface 331 and/oredge 332 of the sidewall of the constraining member 320 and the proximalsection 342 of the engagement component 340, thereby securing, engaging,or grasping the stent 200 therebetween.

Further, in some embodiments, the engagement component 340 can have anouter profile or diameter that is sized about equal to or greater thanan inner profile or inner diameter of the lumen of the constrainingmember 320. The relative sizing of the profiles of the engagementcomponent 340 and the constraining member 320 can be configured suchthat the engagement component 340 can be positioned axially adjacent tothe constraining member 320 in order to “pinch,” secure, grasp, orengage the first portion 206 of the stent 200 in a press or interferencefit. The outer profile of the engagement component 340 can also beconfigured to be sized less than the inner profile of the lumen of theconstraining member 320 if the stent thickness is sufficient to createan interference or otherwise restrict or slow movement of the engagementcomponent 340 into or through the lumen of the constraining member 320.For example, a collective outer profile of the stent 200 and theengagement component 340 can be sized greater than the inner profile ofthe lumen of the constraining member 320. In some embodiments, thecollective outer profile can be an outside diameter calculated by addingthe outside diameter of the engagement component 340 and two times thethickness of the stent 200. However, in other embodiments the outer andinner profiles (which can be measured as a size or shape of a crosssection of the corresponding component(s)) can be noncircular, compriseone or more radial protrusions, or otherwise comprise shapes that areother than circular or rounded.

Additionally, although the embodiment illustrated in FIG. 3A illustratesthat the stent 200 can be secured, grasped, or engaged without havingthe engagement component 340 enter the lumen of the constraining member320, in some embodiments the engagement component 340 extends into or isreceived at least partially in the lumen of the constraining member 320.

FIG. 3B illustrates an alternative embodiment of an stent holdingassembly. As noted herein, the configuration of the core member, stopmember or restraint, and retaining member can be varied in accordancewith several embodiments. FIG. 3B illustrates a stent holding assembly300′ in which a stop member or restraint is formed as a recess 170within a body of a core member 160′. The recess 170 can extendcircumferentially around the core member 160′ to provide a capture area350′ configured to receive at least a portion of the proximal end 202′of the stent 200′. Alternatively, the recess 170 can comprise one ormore indentations into which a portion of the first portion 206′ of thestent 200′ can be received.

Thus, in the illustrated embodiment of FIG. 3B, the core member 160′ canhave a generally constant diameter (or a tapering diameter) and therecess 170 can be configured to receive at least a portion of a firstportion of the stent 200′. The diameter of the core member 160′ can besized larger along an engagement component section 340′ than along aproximal section that extends within a lumen of a constraining member320′. However, the relative diameters of the sections of the core member160′ can be varied and configured in relation to the inner diameter orinner profile of the constraining member 320′, as discussed similarlyabove with respect to FIG. 3A. As with the embodiments discussed above,the stent holding assembly 300′ can cooperatively engage, secure, orgrasp a first portion 206′ of the stent 200′ in order to providesuperior control of the stent 200′ during the operation.

Referring again to FIG. 2, embodiments of the system 100 can beconfigured such that the constraining member 320 can be removablycoupled relative to the core member 160 via a removable, disengageableor breakable coupling 360 (or otherwise selectively longitudinallymoveable, adjustable or retractable relative to the core member 160).The coupling 360 is located preferably near the proximal end 162 of thecore member 160, or at another location on the core member that isaccessible to the clinician outside of the patient's body, proximal ofthe hub 122 or other proximal end portion of the catheter 110. Theconstraining member 320 can extend distally from a proximal end 322thereof at the coupling 360 to a distal end 324 that is located slightlyproximal of (or overlying) the engagement component 340.

A longitudinal or axial position of the constraining member 320 relativeto the core member 160 can be maintained or modified by means of thecoupling 360. The coupling 360 can be located at a proximal locationthat is outside of a body lumen such that a clinician can actuate thecoupling 360 to either maintain or change the relative axial positioningof the constraining member 320 relative to the core member 160.Accordingly, in some embodiments, a clinician can disengage or break abond between the coupling 360 and the constraining member 320 in orderto move the distal end 324 of the constraining member 320 relative tothe core member 160. The clinician can therefore maintain an engagement,securement, or grasp of the stent using the stent holding assembly untilthe stent is positioned at a desired location at the treatment site.Once the stent is in the desired location and properly landed, theclinician can thereafter disengage and release the stent by actuatingthe coupling 360 to proximally withdraw the constraining member 320relative to the core member 160 (or to enable the subsequent proximalwithdrawal of the constraining member).

Further, in some embodiments, the coupling 360 and the constrainingmember 320 can be configured with one or more stop points along a rangeof longitudinal movement of the constraining member 320 relative to thecore member 160. Such stop points can control the relative axialmovement between the constraining member 320 and the core member 160,causing the constraining member to stop at one or more desiredlocations. For example, a first stop point can be provided wherein theconstraining member 320 is in an engaged position (e.g., wherein thefirst portion of the stent is gripped by the stent holding assembly300). The first stop point may indicate tactilely to the clinician thatthe constraining member 320 is positioned to grip the first portion ofthe stent. Instead of or in addition to the first stop point, a secondstop point can be provided that tactilely signals to the clinician thatthe constraining member 320 has been proximally retracted relative tothe core member 160 and/or stop member by a distance that is sufficientto ensure that the stent has been be released from the stent holdingassembly.

The embodiments disclosed herein provide useful advantages. In additionto those discussed herein, the stent holding assembly can provide asystem with superior flexibility and therefore lower the delivery forcenecessary to advance the system to the treatment site. To some extent,the stent holding assembly retains a portion of the stent in a collapsedconfiguration which will tend to lessen the amount of frictionalengagement between the stent and the inner surface of the catheter,further decreasing the delivery force required.

Moreover, as discussed further herein, some embodiments can provide fora delivery system in which the distal end of the stent automaticallyexpands upon exiting the distal end of the catheter, thereby eliminatingthe need for structure that controls the expansion characteristics ofthe distal end of the stent. For example, some embodiments disclosedherein would not require a distal cover that would have to be rotated orotherwise moved to disengage from the distal end of the stent.

Furthermore, embodiments of the stent holding structure can enable aclinician to recapture, collapse, withdraw, or resheath the stent towithin the catheter after partial expansion of the stent. Even insituations where the entire stent has exited the catheter lumen, someembodiments of the stent holding structure disclosed herein can enablethe clinician to recapture, collapse, withdraw, or resheath the firstportion of the stent and therefore the entire stent into the catheterlumen so that the core assembly can be entirely withdrawn or to allowthe stent to be repositioned and landed again at a desired location atthe treatment site.

As noted above, the engagement component of the core assembly can beformed integrally with the core member as a single, continuous piece ofmaterial or formed separately from the core member and coupled thereto.In some embodiments, the engagement component can be rotatably coupledto the core member.

For example, referring to FIGS. 4A-B, alternative embodiments of theengagement component are shown. As shown in FIG. 4A, similarly to FIG.3A, core assembly 500 comprises a constraining member 502, a distalcover 504, an engagement component 506, a core member 508, and a stent510. The engagement component 506 can be formed from a single,continuous piece of material with the core member 508, as discussedabove with respect to some embodiments.

However, FIG. 4B illustrates another core assembly 540 that comprises aconstraining member 542, a distal cover 544, an engagement component546, and a core member 548. The engagement component 546 is formedseparately from the core member 548. The engagement component 546 canoptionally be configured to rotate with respect to the core member 548.Accordingly, in the core assembly 540, the core member 548 can rotatefreely within the constraining member 542, the engagement component 546,and the stent 550. In some such embodiments, a distal tip assembly 552of the core assembly 540 can be rotatably coupled relative to the coremember 548, which can allow the core member 548 to also rotate freelyrelative to the distal tip assembly 552 instead of or in addition to theengagement component 546 and stent 550.

In embodiments using a rotatable engagement component, the core assemblycan exhibit improved flexibility and also reduce torsional stress on thestent mounted thereon. Accordingly, while the core assembly is beingdelivered to the treatment site, the rotational freedom of the coremember can allow the core member to adjust as it traverses tortuouspathways without transferring a torque to the stent. This enhancedrotatability can reduce “whipping.” Further, the improved flexibility ofthe core assembly can also reduce the required delivery force.

Additionally, in some embodiments, the rotatable engagement componentcan be rotatably coupled relative to the core member while the distaltip assembly is fixedly coupled relative to the core member such thatthe distal tip assembly and the core member rotate as a unit. In suchembodiments, the rotatability of the engagement component can beindirectly affected via the contact of the stent with the distal tipassembly and the engagement component. Although the stent may not berotatably fixed relative to the distal tip assembly, the interactionbetween the distal tip assembly and the stent may create some resistanceto rotation of the stent relative to the core member that wouldotherwise be freely permitted at the interconnection of the engagementcomponent and the core member. However, once the distal tip assemblyexits the catheter and the distal end of the stent is allowed to expand,the core member can freely rotate relative to the engagement componentand the stent.

In accordance with aspects of some embodiments, the engagement componentcan also be configured to slide longitudinally relative to the coremember, instead of or in addition to any rotational capability. Forexample, the engagement component and the core member can be configuredsuch that the core member comprises one or more protrusions or limitsagainst which the engagement component can abut to limit thelongitudinal movement (proximal or distal) of the engagement component.

The engagement component preferably comprises a relatively soft orcompressible cylindrical member, and can be formed from a suitablepolymer or elastomer. In some embodiments, the outside diameter of theengagement component is preferably sufficiently small relative to theinside diameter of the catheter to inhibit the engagement component fromgripping or urging the stent against the inner wall of the catheter andthereby generating significant friction between the stent and catheter.For example, as illustrated in FIG. 1, the engagement component 340 canleave sufficient radial space between the outer surface of theengagement component 340 and an inner surface or wall 118 of thecatheter 110 to allow the stent wall to move radially between theengagement component 340 and catheter inner surface 118 when otherwiseunconstrained. Alternatively, the engagement component 340 may be sizedand configured to grip the stent 200 against the inner surface 118 ofthe catheter 110.

In the depicted core assembly 140, the constraining member 320 and theengagement component 340 can grip the stent 200 to facilitate deliveryof the stent 200 through the lumen 116 of the catheter 110, andresheathing of the stent 200 when partially expanded, while completelyor substantially isolating the catheter 110 from the grip forcesinvolved in gripping the stent 200 by the core assembly 140. In thismanner, the core assembly 140 may securely grip the proximal end of thestent 200—securely enough even to facilitate resheathing—withoutgenerating high radial friction forces between the stent 200 and theinner surface 118 of the catheter 110 that can impede advancement of thestent through the catheter 110. Instead, only relatively light radialfrictional forces may exist between the stent 200 and the catheter 110,generated by the stent self-expanding against the inner surface 118,that do not significantly impede axial advancement of the stent 200within the lumen 116 of the catheter 110.

It may also be observed that the stent delivery system 100 can grip thestent 200 radially and/or axially between components that do not (orneed not) move with respect to each other during axial movement of thestent within the lumen 116 of the catheter 110, thereby reducing thefriction that may arise between two components (the core assembly 140and the catheter 110) that can move with respect to each other by asignificant distance during delivery of the stent 200. The catheter 110may remain relatively stationary within the patient's vasculature whilethe core assembly 140 and stent 200 are advanced to and/or through thedistal end of the catheter 110. During this advancement, theconstraining member 320 and the engagement component 340 may remainstationary with respect to each other, and either one or both remainstationary with respect to the stent 200.

Structures other than the herein-described embodiments of theconstraining member 320 and the engagement component 340 may be used inthe core assembly 140 to move the stent 200 along the catheter 110. Forexample, the constraining member 320 and the engagement component 340may be omitted and the proximal bumper 220 employed for that purpose.Instead of, or in addition to, the bumper 220, additional pads orbumpers may be mounted on the core member 160, underlying the stent 200and configured to cooperate with the radially adjacent portions of thecatheter sidewall to grip the stent 200 and facilitate movement alongthe catheter 110.

In accordance with some embodiments, the distal tip assembly of the coreassembly can comprise a distal cover configured to reduce frictionbetween the stent (e.g., the distal portion or distal end thereof) andthe inner surface of the catheter. The distal tip assembly can beconfigured to comprise either or both the distal tip structure and thedistal cover.

Some embodiments can be provided in which the distal cover provides arestrictive force that aids in maintaining the distal portion of thestent in a collapsed configuration until released by the clinician.However, the distal cover of other embodiments disclosed herein does noton its own provide a restraining force to maintain the stent in acollapsed diameter.

For example, the distal cover can be configured as a lubricious,flexible structure having a free first end or section that can extendover at least a portion of the stent and/or intermediate portion of thecore assembly and a fixed second end or section that can be coupled tothe distal tip structure and/or the core member at an attachment point.The second section may be coupled directly to the core member orindirectly to the core member, for example by being coupled to thedistal tip structure. The distal cover can have a first or deliveryposition, configuration, or orientation (see, e.g., FIGS. 1, 2, 4A, 4B,5A, 5B, 6, 13A, 13B) in which the distal cover can extend proximallyrelative to the distal tip structure or the attachment point and atleast partially surround or cover a distal portion of the stent.Further, the distal cover can be movable from the first or deliveryorientation to a second or resheathing position, configuration, ororientation (see, e.g., FIGS. 12B-12C, 13-17) in which the distal covercan be everted such that the first end of the distal cover is positioneddistally relative to the second end of the distal cover to enable theresheathing of the core assembly 140, either with the stent 200 held bythe stent holding assembly 300, or without the stent.

FIGS. 5A and 5B depict embodiments of the distal cover 400. Theembodiments of FIGS. 5A and 5B can be similar to each other instructure, function and method of use, except for the manner in whichthe cover 400 is attached to the core assembly 140. Accordingly, in thediscussion herein of the distal cover 400/400′, any mention of acomponent having a reference numeral used in FIG. 5A (e.g. 420) shouldbe understood to include the corresponding “prime” reference numeralused in FIG. 5B (e.g. 420′), and to apply with equal force to thecomponent so designated in FIG. 5B, and vice versa.

Referring to FIGS. 5A-5B, the core assembly 140 may include the distalcover 400 which, as noted above, can be configured to reduce radialfriction between the stent 200 (e.g., the distal portion 210 or distalend 204 thereof) and the inner surface 118 of the catheter 110. Thedistal cover 400 may include a free first section or end 420 and a fixedsecond section or end 440. As illustrated, the second section 440 iscoupled indirectly to the core member 160 via the distal tip structure182, which is discussed further below.

Further, as shown in FIGS. 5A-5B, at least a portion of the distal cover400 can at least partially extend or be interposed radially between thedistal portion 210 of the stent 200 and the inner surface 118 of thecatheter 110 in the first position, configuration, or orientation. Inthe first orientation, the first section 420 of the distal cover 400 canextend from the second section 440 in a proximal direction to a pointwhere the first section is interposed between the distal portion 210 ofthe stent 200 and the inner surface 118 of the catheter 110. In thisorientation, the first section of the distal cover can take on a“proximally oriented” position or configuration.

The core assembly 140 shown in FIGS. 5A-5B can operate as illustrated inFIGS. 12A-12C. Referring to FIGS. 12A-12C, the core assembly 140 can bedistally advanced until the distal portion 210 of the stent 200 ispositioned distally beyond the distal end 114 of the catheter 110 topermit expansion of the distal portion 210 of the stent 200 into a lumen104 of the blood vessel 102. As the distal portion 210 of the stent 200expands, it can cause the distal cover 400 to be opened or moved fromthe first orientation. Because the stent 200 can foreshorten as itexpands, the stent 200 can withdraw from engagement with the distalcover 400, as shown in FIG. 12A.

After the distal cover 400 has become disengaged from the stent 200 toreach the state shown in FIG. 12A, the cover can proceed to the secondorientation as shown in FIG. 12B or 12C, as oncoming blood flow urgesthe first section 420 distally. Alternatively, the distal cover 400 canremain substantially in the disengaged, distally-extending configurationshown in FIG. 12A until the core assembly 140 is withdrawn proximallyinto the catheter 110, at which point the distal end of the catheter 110can force the approaching first section 420 of the cover 400 to evert orotherwise take on the second configuration as shown in FIG. 15 or 17. Ineach case, the distal cover 400 can move toward an everted position orconfiguration in which the first section 420 of the distal cover 400 isflipped, everted or rotated to extend in a distal direction or in a“distally oriented” position or configuration. In some embodiments of adistally-oriented second configuration, all or at least a portion of thefirst section 420 is located distal of all or at least a portion of thesecond section 440.

The stent 200 can be further unsheathed (as shown in FIG. 13) andsubsequently released (as shown in FIG. 16), or the stent 200 can beretracted and withdrawn back into the catheter 110 (as shown in FIG.14-15), if needed. In either situation, when the distal portion of thecore assembly 140 is withdrawn into the lumen of the catheter 110, thedistal cover 400 can be retracted into the catheter 110 in the secondposition, configuration, or orientation, in which the distal cover 400can be at least partially everted, as shown in FIGS. 14-15 and 17. Thiscan facilitate complete resheathing of the stent 200 and/or the coreassembly 140 within the catheter 110.

In some embodiments, in the first orientation, the first section 420 ofthe distal cover 400 is positioned outside of a radial space 600 locatedbetween the tip assembly 180 and the catheter 110, as shown in FIG. 5.The distal cover 400 can extend proximally from the distal portion orthe tip assembly 180 and from the radial space 600 between the distalportion or tip assembly 180 and the catheter 110. Additionally, in somesuch embodiments, in the second orientation, the first section 420 ofthe distal cover 400 extends distally through the radial space 600 uponretraction of the core assembly 140 into the catheter 110, as shown inFIGS. 15 and 17.

Further, in some embodiments, in the first orientation, at least aportion of the distal cover 400 can extend into a radial space 604within the catheter lumen 116 located between a distal end 612 of theintermediate portion 614 of the core member 160 and the distal end 114of the catheter 110. For example, referring to FIGS. 5A-B, the firstsection 420 of the distal cover 400 can extend or be interposed radiallybetween the distal end 612 of the intermediate portion 614 and the innersurface 118 of the catheter 110. Additionally, in some embodiments, inthe second orientation, the first section 420 of the distal cover 400 nolonger extends or is no longer interposed radially between the distalend 612 of the intermediate portion 614 and the inner surface 118 of thecatheter 110 (and the first section 420 can be located distally of suchlocation), upon retraction of the core assembly 140 into the catheter110, as shown in FIGS. 15 and 17.

Further, in some embodiments, the first section 420 of the distal cover400 can radially overlap with the distal end 204 of the stent 200 at anoverlap point 620 along the core member 160. As illustrated in FIGS.5A-B and 12, the overlap point 620 can be located along the core member160 proximal to the tip assembly 180. In some embodiments, the overlappoint 620 can be spaced about 5 mm to about 12 mm from the proximal endof the distal tip structure 182. In some embodiments, the overlap point620 can be spaced about 6 mm to about 10 mm from the proximal end of thedistal tip structure 182. Further in some embodiments, the overlap point620 can be spaced about 8 mm from the proximal end of the distal tipstructure 182. The overlap point 620 can be located at or near thedistal end 612 of the intermediate portion 614 of the core member 160,or at any location along the core member 160 that underlies an overlapof the (first section 420 of the) distal cover 400 over the stent 200when the core assembly 140 is in its pre-deployment configuration shownin FIGS. 1-5B and 13A-13B. Additionally, in some such embodiments, inthe second orientation, the first section 420 of the distal cover 400 nolonger overlaps with the (distal end 204 of) the stent 200 at theoverlap point 620 (and the first section 420 can be located distally ofsuch location), upon retraction of the core assembly 140 into thecatheter 110, as shown in FIGS. 15 and 17.

In the second orientation, as shown in FIGS. 12A-13, there is no longerradial overlap of the stent 200 and the cover 400 at the overlap point620 or at the distal end 612 of the intermediate section 614. Thus,after disengagement of the distal cover 400 from the stent 200, the coreassembly 140 can be proximally withdrawn into the catheter 110 and thedistal cover 400 will generally extend in a distal direction away fromthe overlap point 620. As also shown in FIG. 14-15, at such time thatthe stent 200 is resheathed or withdrawn into the catheter 110 afterpartial expansion, the stent 200 and the distal cover 400 will notoverlap at the overlap point 620. Thus, the distal cover 400 will notoverlap the stent 200 or the overlap point 620 after at least partialexpansion of the stent 200 when the core assembly 140 is withdrawn intothe catheter 110. Further, once the distal cover 400 is disengaged, theintermediate portion 614 of the core member 160 can be positionedradially adjacent to the distal end 114 of the catheter 110 with thedistal cover 400 being positioned outside of the radial space 604between the intermediate portion 614 and the catheter 110. Accordingly,the movement and configuration of the distal cover 400 can enable thecore assembly 140 to provide radial clearance between the core member160 or the intermediate portion 614 and the catheter 110 forfacilitating resheathing of the core member 160, as shown in FIGS. 14-15and 17.

The distal cover can be coupled relative to the core member. The distalcover can be bonded to the core member and/or the tip assembly 180 ofthe core assembly. In some embodiments, the distal cover can be threadedinto a coil of the tip assembly 180. In the embodiment shown in FIG. 5A,the distal cover 400 can be coupled directly to the distal tip structure182 and indirectly coupled to the core member 160. In the embodiment ofFIG. 5A, the distal tip structure 182 is rigidly coupled to the coremember 160. However, the distal tip structure 182 can also be movablerelative to the core member 160, to provide relative rotation or slidingalong the core member 160, as discussed below with regard to FIG. 5C.

For example, the distal cover 400 and/or the distal tip structure 182can be configured to rotate about the core member 160. For example, anend of the distal cover 400 can be rotatably coupled with respect to thecore member 160. Thus, the stent 200 can be configured to rotate aboutthe core member 160 at least in part by virtue of the rotatable couplingof the distal cover 400. Accordingly, in some embodiments, the stent canrotate with respect to the core member 160 while minimizing anytorsional stresses on the stent.

In the embodiment of FIG. 5A, the distal cover 400 comprises a shrinktube 460 configured to shrink and adhere the second section 440 to thedistal tip structure 182. Alternatively, the second section 440 of thedistal cover 400 can be coupled to the distal tip structure 182 viaother devices or attachment means, including, but not limited tomechanical fasteners, welding techniques, adhesives, heat bonding,combinations thereof, or the like. In yet another alternative, thesecond section 440 can be coupled directly to a distal portion or thedistal end 164 of the core member 160 itself using any suitableattachment.

In some embodiments, the distal tip structure 182 can comprise at leastone member that can be oriented generally transverse or parallel to thecore member. For example, the tip structure 182 can comprise a coil(s),a circumferentially-extending band(s) of material, a clamp(s), and/orother structures that can pass smoothly within a vessel at the distalportion of the core member. Further, the at least one member cancomprise at least one segment of the coil or other structure. Accordingto some embodiments, the distal cover 400 can be coupled to the distaltip structure 182 by virtue of forming an enclosure that encloses the atleast one member. For example, the distal cover 400 can form anenclosure that encloses at least one coil segment of the distal tipstructure 182 by virtue of at least partially wrapping around thesegment.

FIG. 5B illustrates another embodiment of a core assembly 140′. The coreassembly 140′ comprises a core member 160′, a distal tip assembly 180′(having a distal tip structure 182′ in the form of a coil), and a distalcover 400′. The distal cover 400′ comprises a free first section 420′and a fixed second section 440′. The second section 440′ is attached tothe coil of the distal tip structure 182′ by passing or being loopedbetween adjacent windings of the coil (or otherwise through a side ofthe coil or around one or more windings of the coil), as illustrated.The second section 440′ can comprise a looped portion 442′ that extendsbetween the adjacent coil windings and proximally back into contact withanother portion of the second section 440′. The overlapping aspects ofthe looped portion 442′ and the second section 440′ can be fused orotherwise joined or adhered to each other to securely attach the distalcover 400′ to the distal tip structure 182′. Other components of thecore assembly 140′ and catheter 110′ are labeled similarly to FIG. 5A,as illustrated.

FIG. 5C is a rear perspective view of a distal cover 400″. The distalcover 400″ can be similar in structure, function and method of use tothe distal cover 400 (e.g., as shown in FIG. 5A) and/or the distal cover400′ (e.g., as shown in FIG. 5B), but with additional or substitutedstructures, functions and uses as described herein. The distal cover400″ can be used in place of the distal covers 400/400′ in constructingany embodiment of the core assembly 140. The distal cover 400″ can becoupled to a distal tip assembly 180″ in a manner similar to thatillustrated in FIG. 5B. However, in this embodiment, the distal tipassembly 180″ comprises a distal tip structure 182″ that islongitudinally and/or rotatably movable relative to the core member160″.

In some embodiments, the core member 160″ can comprise an proximal stopmember or restraint 430″ and a distal stop member or restraint 432″. Theproximal restraint 430″ and the distal restraint 432″ can be configuredto limit the range of sliding movement of the distal tip structure 182″.The proximal restraint 430″ and the distal restraint 432″ can be spacedapart from each other along the core member 160″ by a distance thatpermits longitudinal movement of the tip structure 182″ relative to thecore member 160″. In some embodiments, the restraints 430, 432 permitsubstantially zero longitudinal movement of the tip structure 182″ andcover 400″ but do allow these components to rotate about the core member160″.

The distal tip structure 182″ can comprise an inner lumen that receivesthe core member 160″ therein such that the distal tip structure 182″ canslide and/or rotate relative to the core member 160″. For example, someembodiments of the distal tip structure 182″ can comprise a coil. Thus,the distal cover 400″ can rotate and/or slide relative to the coremember 160″. Such movement can allow the distal cover 400″ to move orrotate with the stent during delivery to reduce stresses and pushingforce as the core assembly 140″ traverses the vasculature of thepatient.

The distal cover can be one or more strips, wings, or elongate portionsthat are coupled to the tip assembly and/or core member of the coreassembly. In some embodiments, the distal cover comprises no more thantwo elongate strips, wings, or elongate portions. The strips, wings, orelongate portions can be formed as separate components that are coupledto the core assembly. Further, the strips, wings, or elongate portionscan also be formed from a single, continuous piece of material that iscoupled to the core assembly. The strips, wings, or elongate portionscan have free first ends, as well as second ends that are coupled to thecore assembly. The free first ends can cover at least a portion of thestent distal portion during delivery of the stent. Further, when thecore assembly is proximally withdrawn into the catheter, the strips,wings, or elongate portions can be everted, such that free first ends ofthe strips, wings, or elongate portions are drawn together distal to thesecond ends.

For example, the distal cover can be manufactured or otherwise cut froma tube of the material selected for the distal cover. As illustrated inFIGS. 5-6, in some embodiments, the first section 420 may be formed asmultiple longitudinal strips cut from the tube, and the second section440 may be an uncut length of the tube. Accordingly, the tubular secondsection 440 and the proximally extending strips of the first section 420may form a single, integral device or structure.

In some embodiments, the distal cover 400 may comprise a tube and thefirst section 420 can include two or more semi-cylindrical or partiallycylindrical strips or tube portions separated by a corresponding numberof generally parallel, longitudinally oriented cuts or separationsformed or otherwise positioned in the sidewall of the tube. Therefore,when in the pre-expansion state, as shown in FIGS. 1, 2, 4, 5 and 6, thefirst section 420 may generally have the shape of a longitudinally splitor longitudinally slotted tube extending or interposed radially betweenthe outer surface 208 of the stent 200 and the inner surface 118 of thecatheter 110.

In various embodiments, the strips, wings, or elongate portions of thefirst section 420 may collectively span substantially the entirecircumference of the outer surface 208 of the stent 200 (e.g., where thecuts between the strips are splits of substantially zero width), or besized somewhat less than the entire circumference (e.g., where the cutsbetween the strips are slots having a nonzero width). In accordance withsome embodiments, the width of the strips, wings, or elongate portionsof the first section 420 can be between about 0.5 mm and about 4 mm. Thewidth can be about 0.5 mm to about 1.5 mm. In accordance with someembodiments, the width can be about 1 mm.

The strips, wings, or elongate portions of the first section 420 canalso extend longitudinally over at least a portion of the distal portionof the stent. In some embodiments, the first section 420 can extendbetween about 1 mm and about 3 mm over the distal portion of the stent.Further, the first section 420 can also extend between about 1.5 mm andabout 2.5 mm over the distal portion of the stent. In accordance withsome embodiments, the first section 420 can extend about 2 mm over thedistal portion of the stent.

The first section 420 and the second section 440 can define a totallength of the distal cover 400. In some embodiments, the total lengthcan be between about 4 mm and about 10 mm. The total length can also bebetween about 5.5 mm and about 8.5 mm. In some embodiments, the totallength can be about 7 mm.

The strips of the first section 420 may be of substantially uniformsize. For example, the first section 420 can comprise two stripsspanning approximately 180 degrees each, three strips spanningapproximately 120 degrees each, four strips spanning approximately 90degrees each, or otherwise be divided to collectively cover all or partof the circumference of the stent, etc. Alternatively, the strips maydiffer in angular sizing and coverage area without departing from thescope of the disclosure. In one embodiment, only two strips or tubeportions are employed in the first section 420. The use of only twostrips can facilitate radial expansion, distal movement and/or fold-overor everting of the first section 420, as discussed herein, whileminimizing the number of free or uncontained strips in the blood vessellumen and any potential for injuring the vessel by virtue of contactbetween a strip and the vessel wall.

In accordance with some embodiments, at or near the distal end 204 ofthe stent 200, the first section 420 of the distal cover 400 may beconfigured to evert or otherwise fold over and/or within itself, therebycreating a folded portion 480 extending or interposed radially betweenthe outer surface 208 of the stent 200 and the inner surface 118 of thecatheter 110, as shown in FIGS. 5A-B. As illustrated, the folded portion480 can have an outer layer 482 and an inner layer 484, where the outerlayer 482 is radially adjacent the inner surface 118 of the catheter 110and the inner layer 484 is radially adjacent the outer surface 208 ofthe stent 200. In such embodiments, the configuration of the inner layer484, which is radially adjacent to the outer surface 208 of the stent200, can advantageously facilitate expansion of the stent 200 becausethe stent 200 would not need to slide along the inner layer 484.Instead, the inner layer 484 can be everted as the stent expands,thereby reducing any friction between the stent 200 and the distal cover400.

Further, in some embodiments, the distal cover 400 can be configured tofold over itself, in a manner opposite to that shown in FIGS. 5A-B, suchthat layer 482 is the inner layer and layer 484 is the outer layer. Inother embodiments, the first section 420 is not folded, everted, oreverted at all, when in the first or pre-expansion configuration.

The distal cover can be manufactured using a lubricious and/orhydrophilic material such as PTFE or Teflon®, but may be made from othersuitable lubricious materials or lubricious polymers. The distal covercan also comprise a radiopaque material. For example, one or more stripsof Teflon® can be coupled to the core member or distal tip structure inorder to form the distal cover. The distal cover can define a thicknessof between about 0.0005″ and about 0.003″. In some embodiments, thedistal cover can be one or more strips of PTFE having a thickness ofabout 0.001″. The material of the distal cover can also be attached bymeans of another material, such as the shrink tube 460, fitted aroundthe perimeter of the distal cover. The shrink tube 460 can define aradial thickness of between about 0.001″ and about 0.002″. Someembodiments, the radial thickness of the shrink tube is about 0.0015″(based on a tubular shape having an inner diameter of about 0.016″ hadan outer diameter of about 0.019″). Thus, the radial clearance betweenthe distal cover (when everted) and the inner surface of the cathetercan be about 0.002″ and about 0.004″.

When the core assembly 140 is being withdrawn, as shown in FIG. 15 or17, the distal cover 400 can extend distally through the annular spacebetween the distal tip of the core member 160 and the inner surface 118of the catheter 110 and provide a clearance therebetween. The clearancebetween the inner surface 118 and the distal cover 400 (when urgedagainst the distal tip of the core member 160) can be equal to orgreater than the radial clearance between the outer surface of theconstraining member 320 and the inner surface 118 of the catheter 110.Thus, as noted above, if the inner diameter of the catheter 110 is about0.030″ and the outer diameter of the constraining member 320 is about0.025″, the radial clearance between the inner surface 118 and thedistal cover 400 would at least about 0.0025″. Further, as also notedherein, the outer diameter of the distal tip structure 182 can be about0.015″.

In operation, the distal cover 400, and in particular the first section420 or the folded portion 480, can generally cover and protect thedistal end 204 of the stent 200 as the stent 200 is moved distallywithin the catheter 110. The distal cover 400 may serve as a bearing orbuffer layer that, for example, inhibits filament ends 212 of the distalend 204 of the stent 200 (shown schematically in FIGS. 5A-B) fromcontacting the inner surface 118 of the catheter 110, which could damagethe stent 200 and/or catheter 110, or otherwise compromise thestructural integrity of the stent 200. Since the distal cover 400 may bemade of a lubricious material, the distal cover 400 may exhibit a lowcoefficient of friction that allows the distal end 204 of the stent 200to slide axially within the catheter 110 with relative ease. Thecoefficient of friction between the distal cover and the inner surfaceof the catheter can be between about 0.02 and about 0.4. For example, inembodiments in which the distal cover and the catheter are formed fromTeflon®, the coefficient of friction can be about 0.04. Such embodimentscan advantageously improve the ability of the core assembly to passthrough the catheter, especially in tortuous vasculature.

Structures other than the herein-described embodiments of the distalcover 400 may be used in the core assembly 140 to cover the distal endof the stent 200. For example, a protective coil or other sleeve havinga longitudinally oriented, proximally open lumen may be employed.Suitable such protective coils include those disclosed in theincorporated U.S. Patent Application Publication No. 2009/0318947 A1.

Further, as also noted herein, some embodiments can be configured suchthat the distal tip assembly (e.g., the distal tip structure 182) isrotatable and/or axially movable relative to the core member 160.Similarly, in embodiments wherein the distal tip assembly comprises onlythe distal cover 400, although the distal cover 400 can be fixedlycoupled relative to the core member 160, the distal cover 400 can alsobe rotatably and/or axially movably coupled relative to the core member160. Further, when the distal tip assembly comprises both the distal tipstructure and the distal cover, the distal tip assembly can be rotatablyand/or axially movably coupled relative to the core member; however, thedistal tip assembly can also be fixedly coupled to the core member.Thus, as similarly noted above, some embodiments of the distal cover canallow the core member to rotate freely relative to the distal cover andthe stent, thereby avoiding exertion of torsional forces on the stentand/or distal cover as the core assembly is moved through the catheterto the treatment site.

As noted, embodiments of the distal cover can provide variousadvantages. For example, the use of the distal cover can allow the stentholding assembly to be easily urged toward the treatment site within thecatheter. This can advantageously reduce the delivery force required tomove the core assembly through the catheter. In addition, the distal tipassembly can be compactly configured and therefore provide excellentmaneuverability as the stent holding assembly moves through tortuousanatomy. Further, a flexible distal cover such as the depicted distalcovers 400, 400′, 400″ can also allow the distal portion of the stent toopen or expand radially immediately as the distal portion of the stentexits the catheter. The distal cover can be easily urged away from thefirst or encapsulating position or configuration such that the expansionof the stent is not hindered and expansion can be predictable to theclinician. Where employed, this can be a significant improvement overprior art devices that used a relatively rigid tube, such as a coil todistally restrain a distal end of the stent, which could impede or makeunpredictable the proper expansion or deployment of an occluding device,especially large diameter occluding devices.

Further, where the first portion 420 is flexible, evertible, and/orprovides a minimal cross-section, the distal tip assembly can be easilyrecaptured within the catheter to facilitate resheathing for retractionof the core assembly into the catheter. Thus, the catheter can remain inplace and the entire core assembly can be withdrawn therefrom. This canenable the clinician to “telescope” one or more other occluding devices(e.g., delivering more than one occluding device such that it overlapswith another occluding device) without having to remove the catheter,saving time and reducing trauma to the patient.

Referring now to FIGS. 7-11, some embodiments of the stent deliverysystem can also be configured to include multiple stop members orrestraints and engagement components that collectively facilitateengagement between the core assembly and the stent. Further, asdiscussed below, some embodiments can be provided which enable thedelivery system to traverse the tortuous paths while minimizing thelikelihood of damage to the stent.

As shown in FIG. 7, the depicted medical device delivery system 700 cancomprise an elongate tube or catheter 710 which slidably receives a coreassembly 740 configured to carry the stent 800 through the catheter 710.The depicted catheter 710 (see FIGS. 7-9) has a proximal end 712 and anopposing distal end 714 which can be positioned at a treatment sitewithin a patient, an internal lumen 716 extending from the proximal end712 to the distal end 714, and an inner surface 718 facing the lumen716. At the distal end 714, the catheter 710 has a distal opening 720through which the core assembly 740 may be advanced beyond the distalend 714 in order to expand or deploy the stent 800 within the bloodvessel 702. The proximal end 712 may include a catheter hub 722. Thecatheter 710 can define a generally longitudinal axis A-A extendingbetween the proximal end 712 and the distal end 714. When the deliverysystem 700 is in use, the longitudinal axis need not be straight alongsome or any of its length.

The catheter 710 can optionally comprise a microcatheter. For example,the catheter 710 can optionally comprise any of the various lengths ofthe MARKSMAN™ catheter available from Covidien of Mansfield, Mass. USA.The catheter 710 can optionally comprise a microcatheter having an innerdiameter of about 0.030 inches or less, and/or an outer diameter of 3French or less near the distal end 714. Instead of or in addition tothese specifications, the catheter 710 can comprise a microcatheterwhich is configured to percutaneously access the internal carotidartery, or a location within the neurovasculature distal of the internalcarotid artery, with its distal opening 720.

Information regarding additional embodiments of the catheter 710, andadditional details and components that can optionally be used orimplemented in the embodiments of the catheter described herein, can befound in U.S. Patent Application Publication No. US 2011/0238041 A1,published on Sep. 29, 2011, titled Variable Flexibility Catheter. Theentirety of the aforementioned publication is hereby incorporated byreference herein and made a part of this specification.

The core assembly 740 can comprise a core member 760 configured toextend generally longitudinally through the lumen 716 of the catheter710. The core member 760 can have a proximal end or section 762 and aterminal or distal end 764, which can include a tip coil 765. The coremember 760 can also comprise an intermediate portion 766 located betweenthe proximal end 762 and the distal end 764, which intermediate portionis the portion of the core member 760 onto or over which the stent 800is positioned or fitted or extends when the core assembly 740 is in thepre-deployment configuration as shown in FIGS. 7-8.

The core member 760 can generally comprise any member(s) with sufficientflexibility, column strength and thin-ness to move the stent 800 orother medical device through the catheter 710. The core member 760 cantherefore comprise a wire, or a tube such as a hypotube, or a braid,coil, or other suitable member(s), or a combination of wire(s), tube(s),braid(s), coil(s), etc. The embodiment of the core member 760 depictedin FIGS. 7-8 is of multi-member construction, comprising a proximal wire768, a tube 770 (e.g., a hypotube) connected at its proximal end to adistal end of the proximal wire 768, and a distal wire 772 connected atits proximal end to a distal end of the tube 770. An outer layer 774,which can comprise a layer of lubricious material such as PTFE(polytetrafluoroethylene or TEFLON™) or other lubricious polymers, cancover some or all of the tube 770 and/or proximal wire 768. The proximaland/or distal wires 768, 772 may taper or vary in diameter along some orall of their lengths. The proximal wire 768 may include one or morefluorosafe markers 776, and such marker(s) can be located on a portionof the wire 768 that is not covered by the outer layer 774, e.g.,proximal of the outer layer 774. This portion of the wire 768 marked bythe marker(s) 776, and/or proximal of any outer layer 774, can comprisea bare metal outer surface.

The core assembly 740 can further comprise a proximal device interface780 and/or a distal device interface 790 that can interconnect themedical device or stent 800 with the core member 760. The proximaldevice interface 780 can comprise a proximal engagement member 782 thatis configured to underlie the stent 800 and engage an inner wall of thestent. In this manner, the proximal engagement member 782 cooperateswith the overlying inner wall 718 of the catheter 710 to grip the stent800 such that the proximal engagement member 782 can move the stent 800along and within the catheter 710, e.g., as the user pushes the coremember 760 distally and/or pulls the core member proximally relative tothe catheter 710, resulting in a corresponding distal and/or proximalmovement of the stent 800 within the catheter lumen 716.

The proximal engagement member 782 can be fixed to the core member 760(e.g., to the distal wire 772 thereof in the depicted embodiment) so asto be immovable relative to the core member 760, either in alongitudinal/sliding manner or a radial/rotational manner.Alternatively, as depicted in FIGS. 7-8, the proximal engagement member782 can be coupled to (e.g., mounted on) the core member 760 so that theproximal engagement member 782 can rotate about the longitudinal axisA-A of the core member 760 (e.g., of the distal wire 772), and/or moveor slide longitudinally along the core member. In such embodiments, theproximal engagement member 782 can have an inner lumen that receives thecore member 760 therein such that the proximal engagement member 782 canslide and/or rotate relative to the core member 760. Additionally insuch embodiments, the proximal device interface 780 can further comprisea proximal restraint 784 that is fixed to the core member 760 andlocated proximal of the proximal engagement member 782, and/or a distalrestraint 786 that is fixed to the core member 760 and located distal ofthe proximal engagement member 782. The proximal and distal restraints784, 786 can be spaced apart along the core member 760 by a longitudinaldistance that is greater than the length of the proximal engagementmember, so as to leave one or more longitudinal gaps 787 between theproximal engagement member 782 and one or both of the proximal anddistal restraints 784, 786, depending on the position of the proximalengagement member between the restraints. When present, the longitudinalgap(s) 787 allow the proximal engagement member 782 to slidelongitudinally along the core member 760 between the restraints 784,786. The longitudinal range of motion of the proximal engagement member782 between the restraints 784, 786 is approximately equal to the totallength of the longitudinal gap(s) 787.

Instead of or in addition to the longitudinal gap(s) 787, the proximaldevice interface 780 can comprise a radial gap 788 (see FIG. 8) betweenthe outer surface of the core member 760 and the inner surface of theproximal engagement member 782. Such a radial gap 788 can be formed whenthe proximal engagement member 782 is constructed with an inner luminaldiameter that is somewhat larger than the outer diameter of thecorresponding portion of the core member 760. When present, the radialgap 788 allows the proximal engagement member 782 to rotate about thelongitudinal axis A-A of the core member 760 between the restraints 784,786. The presence of longitudinal gaps 787 of at least a minimal size oneither side of the proximal engagement member 782 can also facilitatethe rotatability of the proximal engagement member.

One or both of the proximal and distal restraints 784, 786 can have anoutside diameter or other radially outermost dimension that is smallerthan the outside diameter or other radially outermost dimension of theproximal engagement member 782, so that one or both of the restraints784, 786 will tend not to contact the inner surface of the stent 800during operation of the core assembly 740.

In the proximal device interface 780 shown in FIGS. 7-8, the stent 800can be moved distally or proximally within the catheter 700 via theproximal engagement member 782. During distal movement, the distal endof the proximal restraint 784 bears on the proximal end of theengagement member 782, and the engagement member urges the stent 800distally via frictional engagement with the inner surface of the stent800 (assisted by the overlying catheter 710). During proximal movement,the proximal end of the distal restraint 786 bears on the distal end ofthe engagement member 782, which in turn moves the stent 800 proximallyvia such frictional engagement. Proximal movement of the stent 800relative to the catheter 710 can be employed when withdrawing orre-sheathing the stent 800 back into the distal end 714 of the catheter710, as will be discussed in greater detail below. When the stent 800has been partially deployed and a portion of the stent remains disposedbetween the proximal engagement member 782 and the inner wall of thecatheter, the stent 800 can be withdrawn back into the distal opening720 of the catheter by moving the core assembly 740 (including theengagement member 782) proximally relative to the catheter 710 (and/ormoving the catheter 710 distally relative to the core assembly 740).Re-sheathing in this manner remains possible until the engagement member782 and/or catheter 710 have been moved to a point where the engagementmember 782 is beyond the distal opening 720 of the catheter 710 and thestent 800 is released from between the member 782 and the catheter 710.

Optionally, the proximal edge of the proximal engagement member 782 canbe positioned just distal of the proximal edge of the stent 800 when inthe delivery configuration shown in FIGS. 7-8. In some such embodiments,this enables the stent 800 to be re-sheathed when as little as about 3mm of the stent remains in the catheter 710. Therefore, with stents 800of typical length, resheathability of 75% or more can be provided (i.e.the stent 800 can be re-sheathed when 75% or more of it has beendeployed).

The distal device interface 790 can comprise a distal engagement member792 that can take the form of, for example, a distal device cover ordistal stent cover (generically, a “distal cover”). The distal cover 792can be configured to reduce friction between the medical device or stent800 (e.g., the distal portion or distal end thereof) and the innersurface 718 of the catheter 710. For example, the distal cover 792 canbe configured as a lubricious, flexible structure having a free firstend or section 792 a that can extend over at least a portion of thestent 800 and/or intermediate portion 766 of the core assembly 760, anda fixed second end or section 792 b that can be coupled (directly orindirectly) to the core member 760.

The distal cover 792 (e.g., the second end 792 b thereof) can be fixedto the core member 760 (e.g., to the distal wire 772 or distal tip 764thereof) so as to be immovable relative to the core member 760, eitherin a longitudinal/sliding manner or a radial/rotational manner.Alternatively, as depicted in FIGS. 7-8, the distal cover 792 (e.g., thesecond end 792 b thereof) can be coupled to (e.g., mounted on) the coremember 760 so that the distal cover 792 can rotate about thelongitudinal axis A-A of the core member 760 (e.g., of the distal wire772), and/or move or slide longitudinally along the core member. In suchembodiments, the second end 792 b can have an inner lumen that receivesthe core member 760 therein such that the distal cover 792 can slideand/or rotate relative to the core member 760. Additionally in suchembodiments, the distal device interface 790 can further comprise aproximal restraint 794 that is fixed to the core member 760 and locatedproximal of the (second end 792 b of the) distal cover 792, and/or adistal restraint 796 that is fixed to the core member 760 and locateddistal of the (second end 792 b of the) distal cover 792. The proximaland distal restraints 794, 796 can be spaced apart along the core member760 by a longitudinal distance that is greater than the length of thesecond end 792 b, so as to leave one or more longitudinal gaps 797between the second end 792 b and one or both of the proximal and distalrestraints 794, 796, depending on the position of the second end 792 bbetween the restraints. When present, the longitudinal gap(s) 797 allowthe second end 792 b and/or distal cover 792 to slide longitudinallyalong the core member 760 between the restraints 794, 796. Thelongitudinal range of motion of the second end 792 b and/or distal cover792 between the restraints 794, 796 is approximately equal to the totallength of the longitudinal gap(s) 797.

Instead of or in addition to the longitudinal gap(s) 797, the distaldevice interface 790 can comprise a radial gap 798 between the outersurface of the core member 760 (e.g., of the distal wire 772) and theinner surface of the second end 792 b. Such a radial gap 798 can beformed when the second end 792 b is constructed with an inner luminaldiameter that is somewhat larger than the outer diameter of thecorresponding portion of the core member 760. When present, the radialgap 798 allows the distal cover 792 and/or second end 792 b to rotateabout the longitudinal axis A-A of the core member 760 between therestraints 794, 796. The presence of longitudinal gaps 797 of at least aminimal size on either side of the second end 792 b can also facilitatethe rotatability of the distal cover.

One or both of the proximal and distal restraints 794, 796 can have anoutside diameter or other radially outermost dimension that is smallerthan the (e.g., pre-deployment) outside diameter or other radiallyoutermost dimension of the distal cover 792, so that one or both of therestraints 794, 796 will tend not to bear against or contact the innersurface 718 of the catheter 710 during operation of the core assembly740.

With reference now to FIGS. 8-9, it may be observed that the distalrestraint 786 of the proximal device interface 780, and/or the proximaland/or distal restraints 794, 796 of the distal device interface 790,can each optionally comprise a tapered portion 850 and a cylindrical ornon-tapered portion 852. In the proximal device interface 780, thedistal restraint 786 can form a tapered portion 850 that is locateddistal of its non-tapered portion 852, and tapers down in diameter orcross-sectional size as it extends distally, away from the proximalengagement member 782. In the distal device interface 790, the proximalrestraint 794 can form a tapered portion 850 that is located proximal ofits non-tapered portion 852, and tapers down in diameter orcross-sectional size as it extends proximally, away from the distalengagement member 792; the distal restraint 796 can form a taperedportion 850 that is located distal of its non-tapered portion 852, andtapers down in diameter or cross-sectional size as it extends distally,away from the distal engagement member 792. Accordingly, in the depictedembodiment each of the restraints 786, 794, 796 forms a tapered portion850 that tapers radially inwardly as it extends away from its respectiveengagement member 782/792 and/or its respective longitudinal gap(s)787/797.

By incorporating the tapered portion(s) 850, the restraint(s) 786, 794,796 can provide the benefit of relatively large diameter orcross-sectional size in the non-tapered portion 852 (effectivelongitudinal restraint of the engagement member 782/792) and/orrelatively long axial length (secure attachment to the core member 760)without suffering the drawback of increased stiffness or reducedbendability of the core assembly 740 and delivery system 700. This maybe understood best with reference to FIG. 9, which shows the deliverysystem 700 including the core assembly 740 passing through a bend in thevessel 702. In this drawing it can be observed that the tapered portion850 of the distal restraint 786 of the proximal device interface 780provides ample clearance for the sharply bending adjacent portion of thecatheter 710 and stent 800, as compared to a non-tapered restraint ofsimilar length and cross-sectional size or diameter. Accordingly thetapered restraint 786 allows the core assembly 740 and core member 760to bend more sharply (and/or to bend without the restraint contactingthe inner surface of the stent 800) in the vessel 702 than would bepossible with a non-tapered restraint of similar axial length andcross-sectional size or diameter. In this manner the risk of a distalcorner of the restraint 786 impinging on the inner surface of the stent800 and creating a pressure concentration that can require a higher pushforce from the user, is reduced.

With further reference to FIG. 7, in some embodiments the distalrestraint 796 of the distal device interface 790 may have a smaller(maximum) outside diameter or cross-sectional size than the proximalrestraint 794 of the distal interface 790. Such a smaller distalrestraint can help provide radial clearance for the everted first end792 a of the distal cover 792 during retraction into the catheter 710.

FIG. 10 shows an additional embodiment of the core assembly 740 (withthe stent 800) which can be identical in structure, function andmethod(s) of use to any of the other embodiments of the core assembly740 described herein, except as further described as follows. In thisembodiment, the proximal device interface 780 (including for example theproximal engagement member 782 and/or its restraints 784, 786) can belocated in a distal portion of the stent 800, e.g., in the distal halfof the stent 800, overlapping with or just proximal of the distal cover792, or partially or wholly overlapping with the distal cover 792.Further, according to some embodiments, that the proximal deviceinterface 780 be located only in the distal half of the stent 800 doesnot mean that the proximal device interface 780 extends along the entiredistal half, but instead can refer to embodiments in which the proximaldevice interface extends along less than the distal half.

For example, the proximal engagement member 782 can be located so thatits distal end is less than 1 mm proximal of the proximal end of thecover 792, or distal of such location. With the proximal deviceinterface 780 and proximal engagement member 782 so located, the member782 can urge the stent 800 distally primarily by “pulling” the stentfrom a distal portion thereof, applying force to a point or region in adistal portion, or near the distal end, of the stent. When moving orpulling the stent in this fashion, the amount of push force necessary tobe exerted through the core member 760 is reduced because the tendencyof the stent to expand radially (as can occur when it is pushed distallyand longitudinally compressed by a force applied to a point or regionnear the proximal end of the stent) is reduced. Optionally, in theembodiment of FIG. 10 there may be no additional structures proximal ofthe engagement member 782 and/or interface 780 that transmit force fromthe core member 760 or wire 772 to the stent 800.

FIG. 11 depicts an additional embodiment of the core assembly 740 whichcan be identical to the embodiment of FIG. 10, with the addition of asecond proximal device interface 780′ in a proximal portion of the stent800, in addition to the distally located interface 780 described withreference to FIG. 10. The second interface 780′ and/or its engagementmember 782′ can be located in a proximal portion of the stent 800, e.g.,near the proximal end or in the proximal half of the stent 800. In suchan arrangement, both the interfaces 780, 780′ and/or members 782, 782′can urge the stent 200 distally in response to a distal push forceexerted on the core member 760, thereby both “pulling” the stent fromthe distal portion and “pushing” it from the proximal portion. This canalso reduce the amount of push force necessary to be exerted through thecore member 760 to advance the stent into or through the catheter 710.In addition, the interface 780′ and member 782′ when located near theproximal end of the stent 800 can facilitate re-sheathing the stent 800even when most of the stent 800 (e.g., except for the proximal-mostportion thereof) has been deployed.

In the embodiments of FIGS. 10 and 11, any of the embodiments of theproximal device interface 780 and proximal engagement member 782described herein (rotating, non-rotating, sliding, non-sliding, and anyother varieties) can be employed.

FIGS. 1, 7-9, and 12A-18B depict some embodiments and methods of use ofthe stent delivery system 100. First, the catheter 110 can be insertedinto the patient's vasculature via a percutaneous access technique orother suitable method of access. The distal end 114 of the catheter 110is then advanced to a treatment site or location in the blood vessel102. The blood vessel 102 may comprise a vein or artery, such as anartery in a brain or within a cranium of the patient. As previouslymentioned, the catheter 110 can comprise a microcatheter. A guidecatheter can be used instead of or in addition to the catheter 110; forexample, the guide catheter can first be placed in the vasculature sothat it extends part or all of the way to the treatment site and amicrocatheter or other catheter then inserted through the guide catheterto the treatment site.

The treatment location may be near an aneurysm (not shown) formed in awall of the blood vessel 102, and advancing the catheter 110 to thetreatment location may include advancing the distal end 114 and/ordistal opening 120 to a location that is distal of the aneurysm. Suchadvancement of the catheter 110 may include advancing the distal end 114and/or distal opening 120 distally across the ostium or neck of theaneurysm, to the location in the vessel 102 distal of the aneurysm.

Once the catheter 110 has been inserted, it may extend proximally fromthe distal end 114 and/or distal opening 120 at the treatment location,through the vascular access site, to the proximal end 112 and/or hub 122which are preferably situated outside the patient's body.

After the catheter 110 has been placed, the core assembly 140 (with thestent 200 carried thereby) can be inserted, distal end first, into thelumen 116 of the catheter 110 via the hub 122 and/or proximal end 112.Where the distal portion of the core assembly 140 is initially containedwithin an introducer sheath (not shown), the introducer sheath can beinserted partway into the catheter lumen 116 and the core assembly 140is advanced distally through the introducer sheath until the distalportion and stent 200 exit the distal end of the introducer sheath andpass into (direct contact with) the lumen 116 of the catheter 110. Thecore assembly 140 and stent 200 are at that point disposed in thecatheter 110 generally as depicted in FIG. 1, but in a proximal portionof the catheter 110. In particular, the stent 200 and distal portion ofthe core assembly 140 can be positioned in the lumen 116 of the catheter110, with the proximal end 202 of the stent 200 received in theconstraining member 320 and the remaining portions of the stent 200extending distally and generally in contact with the inner surface 118of the catheter except where the first section 420 of the distal cover400 is extending or interposed radially between the distal end 204 ofthe stent 200 and the inner surface 118 of the catheter 110. Further,the core member 160 and constraining member 320 can extend proximally ofthe proximal end 112 and/or hub 122 of the catheter 110 to a locationoutside of the patient's body, so that the coupling 360 and proximalends 162, 322 of the core member 160 and constraining member 320 can beeasily accessed.

Next, the core assembly 140 with the stent 200 can be axially advanceddistally within the lumen 116 of the catheter 110, toward the distal end114 of the catheter 110 and treatment location. Generally, duringadvancement of the core assembly 140 in the catheter 110, theconstraining member 320 and the engagement component 340 can secure,grip, or engage the stent 200 to facilitate urging the stent distallythrough the catheter 110, substantially without transmitting anysecurement forces to the catheter 110 or otherwise independently of thecatheter 110. The constraining member 320 and the engagement component340 can secure, grip, or engage the stent 200 during distal advancementthrough the catheter 110 without relative axial motion between theconstraining member 320 and the engagement component 340, while theconstraining member 320, the engagement component 340, and the stent 200move distally relative to the catheter 110 and the vasculature.

As the stent 200 and distal cover 400 are advanced toward the distal end114 and treatment location, the first section 420 of the distal cover400 remains extending or interposed radially between the outer surface208 and/or distal end 204 of the stent 200 and the inner surface 118 ofthe catheter 110. Thus, the distal cover 400 may inhibit the distal end204 of the advancing stent 200 (e.g., the filament ends 212 thereof)from damaging, abrading, or gouging the catheter 110, and from therebyimpeding progress of the stent 200 along the catheter 110. This may, inturn, avoid damage to the stent 200 such as by longitudinal compressionresulting from high friction generated between the distal end 204 of thestent 200 and the catheter 110 while distally directed force is appliedto the first portions of the stent 200.

Where the treatment location is near an aneurysm and the distal end 114and/or distal opening 120 of the catheter 110 has been advanced to alocation that is distal of the aneurysm, advancement of the coreassembly 140 with the stent 200 toward the distal end 114 and treatmentlocation can include advancing the distal portion of the core assembly140 and the distal end 204 of the stent 200 distally through thecatheter 110 across the ostium or neck of the aneurysm, to a location inthe vessel 102 distal of the aneurysm.

To begin expansion of the stent 200 (see FIG. 12A-12C), the coreassembly 140 may be held stationary and the catheter 110 may bewithdrawn proximally over the stent 200 and distal portion of the coreassembly 140, until the distal end 114 of the catheter 110 is even withor proximal of the distal end 324 of the constraining member 320 or evenwith or proximal of the proximal end 202 of the stent 200 or proximalretaining member 220, as shown in FIG. 13. (Optionally, the coreassembly and stent can be advanced distally while performing this step,instead of or in addition to withdrawal of the catheter.) As a result,the stent 200 (except for the portion retained in the constrainingmember 320) can be released and permitted to expand into engagement withthe inner wall of the blood vessel 102, as shown in FIG. 13. Someembodiments of the stent 200 (such as certain braided stents) canshorten axially while expanding radially. As a result of (i) any axialforeshortening of the stent 200, (ii) radial expansion of the stent 200,and/or (iii) radial expansion of the distal cover 400 in response toradial expansion of the stent 200, the strips or tube portions of thefirst section 420 of the distal cover 400 can disengage from contactwith the distal end 204 of the stent 200, while in some embodimentsseparating and moving radially outward as well.

In some embodiments, as the distal cover 400 disengages from the stent,it unfurls or otherwise unravels from its folded configuration 480 (seeFIGS. 12-13). Once the distal cover 400 disengages or unravels, it nolonger covers the distal end 204 of the stent 200; instead, its firstsection 420 is now spaced distally from the stent distal end 204 asshown in FIGS. 12-13. In this state, the strips or tube portions formingthe proximal end can be free or unconfined within the lumen of the bloodvessel 102. As similarly noted above, the strips or tube portions canhave free first ends, as well as second ends that are coupled to thecore assembly 140. The free first ends can cover at least a portion ofthe stent distal portion during delivery of the stent. Further, when thestent is expanded and/or the core assembly 140 is proximally withdrawninto the catheter, the strips or tube portions can be everted, such thatfree first ends of the strips, wings, or elongate portions are drawntogether distal to the second ends thereof.

The pullback of the catheter 110 (and/or distal movement of the coreassembly 140) and expansion of the stent 200 may be done in multiplediscrete steps. For example, the catheter 110 may initially be pulledback proximally only part of the way to the location depicted in FIGS.12A-12C, and only the distal portion 204 of the stent 200 expanded intoengagement with the vessel wall. Such initial partial expansionfacilitates anchoring the distal portion of the stent in the vessel 102,which in turn facilitates longitudinal stretching or compression of thestent 200 as desired by the clinician during or prior to expansion ofthe remaining portions of the stent 200 into the vessel 102. Initialpartial expansion can also facilitate confirmation by the clinician thatthe distal portion of the stent 200 has “landed” in the desired locationin the vessel 102 (e.g., distal of the neck or ostium of any aneurysmformed in the vessel wall) prior to expansion of the remaining portionsof the stent 200. Generally, where an aneurysm is present in the vessel102, proper placement of the stent 200 can include positioning a distalportion of the stent 200 in the vessel lumen distal of the aneurysm neckand a first portion of the stent in the vessel lumen proximal of theaneurysm neck, such that the stent 200 extends across the neck. Wherethe expanded stent 200 is appropriately configured, it may then performa therapeutic flow-diverting function with respect to the aneurysm.

While the stent delivery system 100 is in the configuration shown inFIG. 13, with the proximal end 202 of the stent 200 retained within theconstraining member 320, the partially expanded stent 200 can beresheathed or retracted proximally into the catheter 110 as shown inFIG. 14-15. The engagement mechanism, e.g., the constraining member 320and the engagement component 340, can secure, grip, or engage the stent200 to a sufficient degree to permit the catheter 110 to be advanceddistally over the partially expanded stent 200 (and/or the core member160 withdrawn proximally relative to the catheter 110) until the stent200 is again positioned in the lumen 116 of the catheter 110. Thus, theengagement mechanism of the core assembly 140 can exert a proximal forceon the stent 200 as the stent 200 is withdrawn or retracted into thecatheter 110.

FIG. 14 shows a first aspect of a process of resheathing the stent 200,in which the stent 200, including the distal end 204, has been drawninto the lumen 116 of the catheter 110. Because the previouslystent-engaging portion (e.g., the first section 420) of the distal cover400 has moved radially outward from the core member 160 and/or distallyrelative to the core member 160, it does not impede the entrance of thedistal portion and distal end 204 of the stent 200 into the distalopening 120 of the catheter 110 during resheathing. Accordingly, theresheathing process of FIG. 14-15 can comprise moving the stent 200(including the distal end 204) into the catheter 110 through the distalopening 120 while the previously stent-engaging portion (e.g., the firstsection 420) of the distal cover 400 is in a second, everted, orresheathing configuration in which the stent-engaging portion isdisposed radially outward from the core member 160 and/or the firstsection 420 of the distal cover 400 is disposed distally relative to thecore member 160, the second section 440, and/or the distal tip structure182, in comparison to a first, encapsulating, or delivery configuration(e.g., FIG. 1) of the stent-engaging portion (e.g., the first section420) of the distal cover 400.

While FIG. 14 illustrates an initial aspect of the resheathing process,FIG. 15 shows a second aspect of the resheathing process currently underdiscussion. In this aspect of the process, the core assembly 140 can bemoved further proximally into the catheter 110 (and/or the catheter 110is moved further distally over the core assembly 140) until the distalcover 400 enters the catheter 110 via the distal opening 120. As notedabove, the first section 420 of the distal cover 400 is preferablysufficiently flexible to evert and thereby attain the second, everted,or resheathing configuration shown in FIG. 14-15. In the second,everted, or resheathing configuration, the first section 420 of thedistal cover 400 can extend generally in a distal direction, away fromthe stent 200, and/or extend distally of the second section 440 of thedistal cover 400. Further, in some embodiments, the first section 420 ofthe distal cover 400 can also radially overlap the distal tip structure182. Instead of or in addition to these aspects of the second, everted,or resheathing configuration, the distal cover 400 can be radially smallenough to extend into the lumen 116 of the catheter 110, eitherpartially as depicted in FIG. 14, or wholly as depicted FIG. 15, and/orthe entire distal cover 400 can be spaced distally from the distal end204 of the stent 200 in the lumen 116 of the catheter 110.

Accordingly, in accordance with some embodiments of methods disclosedherein, when operating the stent delivery system, a clinician can checkthe initial partial expansion of the stent 200 (e.g., as shown in FIGS.12A-13) and, if the initial placement is unsatisfactory or if theinitial expansion of the stent 200 is unsatisfactory, the clinician canrecapture, collapse, withdraw, or resheath the stent 200 into thecatheter 110, as described above with respect to FIGS. 14 and/or 15.After resheathing, the clinician can attempt to land the stent again, asdescribed herein, beginning for example, with the state depicted in FIG.14 or 13, and resulting for example, in the state depicted in FIG. 12A.Resheathing can also be performed, and the stent delivery system 100 andstent 200 removed from the patient entirely, if for example, thedelivery and/or expansion of the stent 200 damages or reveals a defectin, or improper sizing of, the stent 200 or delivery system 100. Afteran initial partial expansion of the stent 200, the depicted coreassembly 140 can optionally be entirely removed with the stent 200 fromthe catheter 110 without need to remove the catheter 110 from the bloodvessel 102. In this manner, access to the treatment site in the bloodvessel 102 can be maintained via the catheter 110 and, if desired,additional attempts to deliver the stent 200 can be made through thecatheter 110.

If the initial expansion of the stent 200 in the vessel 102 issatisfactory, full expansion can be completed to result in the statedepicted in FIG. 16. The coupling 360 is removed, broken, or otherwisedisengaged to permit the constraining member 320 to move relative to thecore member 160. The proximal end 202 of the stent 200 may then bereleased from the constraining member 320 and the engagement component340 by holding the core member 160 stationary and withdrawing theconstraining member 320 proximally relative to the core member 160 andthe stent 200 until the distal end 324 is approximately even with theproximal retaining member 220, or otherwise proximal of the proximal end202 of the stent 200. (If the distal end 114 of the catheter 110 has notyet been withdrawn to a location proximal of the proximal end 202 of thestent 200, that can be done as well.) No longer constrained by theconstraining member 320 and the engagement component 340, the proximalend 202 of the stent 200 can now expand into contact with the wall ofthe vessel 102, as shown FIG. 16. (Note that until this point, accordingto an aspect of some embodiments, the partially expanded stent 200 hadbeen fully resheathable.) Where the vessel 102 includes an aneurysm, theproximal end 202 is preferably located in the vessel 102 proximal of theaneurysm neck following expansion.

Following full expansion of the stent 200, the core assembly 140 can bedrawn back into the catheter 110, as shown in FIG. 17. Both the catheter110 and core assembly 140 can be withdrawn from the patient, eithersimultaneously or sequentially. However, when the stent has beensuccessfully released, the core assembly 140 can also be entirelyremoved from the catheter 110, with the catheter 110 remaining in place,and a second core assembly can be inserted into the lumen. The secondcore assembly can be configured to deliver a second stent to thetreatment site in order to perform, e.g., a telescoping procedure.

In another embodiment of a method, the stent 200 can be initiallypartially expanded (e.g., as shown in FIG. 13) in a blood vessel 102wherein a branch vessel (not shown) joins the blood vessel at a junctionlocated along the portion of the vessel 102 in which the stent 200 hasbeen partially expanded. Patency of the branch vessel can then bechecked by, for example, injecting a contrast agent near the junctionand observing via, for example, fluoroscopy whether the agent can flowfrom the vessel 102 into the branch vessel. Thus it can be determinedwhether a portion of the stent 102 has occluded the branch vessel. If itappears that the branch vessel has been occluded, the stent 200 can berepositioned within the vessel 102 without resheathing, or the stent 200can be resheathed using any of the techniques discussed herein. Afterresheathing, the stent 200 can be partially expanded again, and branchvessel patency checked again.

In the present disclosure, numerous references are made to moving thecatheter 110 axially over the core assembly 140, and moving the coreassembly 140 axially within the catheter 110. Except where specificallynoted to the contrary, all such references to one form of this relativemovement should be understood to include the other as an alternative.

As discussed above, the stent delivery system 100 can also be configuredto allow the clinician to control the articulation and delivery of thesystem by steering a portion of the system. For example, referring toFIGS. 18A-18B, the stent delivery system 100 can optionally include asteerable tip assembly 900. The steerable tip assembly 900 can allow aclinician to avoid perforating or abrading the vessel wall of a vesselbifurcation or a sharp turn in the vessel while performing theprocedure. As noted above, in some embodiments, the steerable tipassembly 900 can include the core member 160, which can have acurvilinear distal end 164. Optionally, in some embodiments, thesteerable tip assembly 900 can be employed with one or more engagementcomponents 340 that are rotatably mounted on the core member 160.Accordingly, the core member 160 can be configured to be steerableduring stent expansion, or when the stent is in the catheter orpartially expanded within the vessel by being rotatable relative to thestent 200, the catheter 110, and/or other components of the stentdelivery system 100.

In use, the clinician can advance the stent delivery system 100 to thetreatment location axially within the vessel 102. In preparation fordeployment and expansion of the stent 200, the clinician can survey thesurrounding vasculature of the treatment site and determine whetherthere is a risk of having the distal end of the core member abrade orperforate a vessel wall as the core member is advanced distally asanticipated during stent expansion or during advancement of the system100 to the treatment location. Generally, the core member 160 and thedistal tip assembly 180 are often advanced distally in the course ofexpanding a stent, so the anticipated distal movement can be thatresulting from stent deployment near a bifurcation or sharp turn in thevessel. If there is a risk that abrasion or perforation of a vessel maytake place, the clinician can carefully land the stent and thereafter(or beforehand) rotate the core member to reorient or redirect thedistal end or point of the core member towards the pathway of the vesseland away from the vessel wall.

The risk of abrasion or perforation can be substantially greater whenthe treatment location is adjacent to a bifurcation or sharp turn in thevessel. For example, FIGS. 18A-18B illustrate a scenario in which anapex 940 of a bifurcation 942 lies in the anticipated path of the distalend 164 of the core member 160. As such, if the distal end 164 isadvanced distally towards the apex 940 in the position, configuration,or orientation shown in FIG. 18A (and especially if the core member anddistal tip are straight and not curved), there is a likelihood that theapex of the bifurcation will be abraded or perforated by the distal tipof the core member.

However, as shown in FIG. 18B, in order to avoid the abrasion orperforation, the distal end 164 of the core member 160 can be rotated toreorient the curved portion of the distal end 164 toward a lower-riskpathway such as a desired branch vessel. The distal end 164 can beformed from a radiopaque material to make the distal end 164 visibleunder electromagnetic radiation or other imaging, and thereforefacilitate recognition by the clinician of the orientation of the distalend 164 with respect to the surrounding vasculature. Having observed theorientation of the distal end 164, the clinician can determine how to“aim” the distal end 164 of the core member 160 to avoid abrasion orperforation of the vessel wall. For example, in accordance with someembodiments, after determining the appropriate direction after viewingthe position of the distal end 164, the clinician can rotate andreorient the distal end 164 to point the core member 160 in a desired orlower-risk direction by rotating a proximal end of the core member 160.Further, as noted herein, rotation of the core member relative to thestent can allow the clinician to avoid dislodging the stent from thevessel wall after initial expansion of the stent and also avoid abrasionor perforation of the blood vessel. In this manner, the stent deliverysystem can advantageously allow a clinician to steer and control thearticulation of the stent delivery system to ensure that the vesselsadjacent to the treatment site are not damaged as the stent is deployedand the core assembly 140 is advanced.

Information regarding additional embodiments of the stent deliverysystem 100, and additional details and components that can optionally beused or implemented in the embodiments of the stent delivery systemdescribed herein, can be found in the above-incorporated U.S. PatentApplication Publications Nos. US 2011/0152998A1 and US 2009/0318947A1.The stent delivery system 100 disclosed herein can optionally be similarto any of the delivery systems disclosed in these publications, exceptas further described herein.

The apparatus and methods discussed herein are not limited to theexpansion and use of an stent or occluding device within any particularvessels, but may include any number of different types of vessels. Forexample, in some aspects, vessels may include arteries or veins. Thevessels may have bifurcations and/or sharp turns. In some aspects, thevessels may be suprathoracic vessels (e.g., vessels in the neck orabove), intrathoracic vessels (e.g., vessels in the thorax), subthoracicvessels (e.g., vessels in the abdominal area or below), lateral thoracicvessels (e.g., vessels to the sides of the thorax such as vessels in theshoulder area and beyond), or other types of vessels and/or branchesthereof.

In some aspects, the suprathoracic vessels may comprise at least one ofintracranial vessels, cerebral arteries, and/or any branches thereof.For example, the suprathoracic vessels may comprise at least one of acommon carotid artery, an internal carotid artery, an external carotidartery, a middle meningeal artery, superficial temporal arteries, anoccipital artery, a lacrimal (ophthalmic) artery, an accessory meningealartery, an anterior ethmoidal artery, a posterior ethmoidal artery, amaxillary artery, a posterior auricular artery, an ascending pharyngealartery, a vertebral artery, a left middle meningeal artery, a posteriorcerebral artery, a superior cerebellar artery, a basilar artery, a leftinternal acoustic (labyrinthine) artery, an anterior inferior cerebellarartery, a left ascending pharyngeal artery, a posterior inferiorcerebellar artery, a deep cervical artery, a highest intercostal artery,a costocervical trunk, a subclavian artery, a middle cerebral artery, ananterior cerebral artery, an anterior communicating artery, anophthalmic artery, a posterior communicating artery, a facial artery, alingual artery, a superior laryngeal artery, a superior thyroid artery,an ascending cervical artery, an inferior thyroid artery, a thyrocervical trunk, an internal thoracic artery, and/or any branchesthereof. The suprathoracic vessels may also comprise at least one of amedial orbitofrontal artery, a recurrent artery (of Heubner), medial andlateral lenticulostriate arteries, a lateral orbitofrontal artery, anascending frontal (candelabra) artery, an anterior choroidal artery,pontine arteries, an internal acoustic (labyrinthine) artery, ananterior spinal artery, a posterior spinal artery, a posterior medialchoroidal artery, a posterior lateral choroidal artery, and/or branchesthereof. The suprathoracic vessels may also comprise at least one ofperforating arteries, a hypothalamic artery, lenticulostriate arteries,a superior hypophyseal artery, an inferior hypophyseal artery, ananterior thalamostriate artery, a posterior thalamostriate artery,and/or branches thereof. The suprathoracic vessels may also comprise atleast one of a precentral (pre-Rolandic) and central (Rolandic)arteries, anterior and posterior parietal arteries, an angular artery,temporal arteries (anterior, middle and posterior), a paracentralartery, a pericallosal artery, a callosomarginal artery, a frontopolarartery, a precuneal artery, a parietooccipital artery, a calcarineartery, an inferior vermian artery, and/or branches thereof.

In some aspects, the suprathoracic vessels may also comprise at leastone of diploic veins, an emissary vein, a cerebral vein, a middlemeningeal vein, superficial temporal veins, a frontal diploic vein, ananterior temporal diploic vein, a parietal emissary vein, a posteriortemporal diploic vein, an occipital emissary vein, an occipital diploicvein, a mastoid emissary vein, a superior cerebral vein, efferenthypophyseal veins, infundibulum (pituitary stalk) and long hypophysealportal veins, and/or branches thereof.

The intrathoracic vessels may comprise the aorta or branches thereof.For example, the intrathoracic vessels may comprise at least one of anascending aorta, a descending aorta, an arch of the aorta, and/orbranches thereof. The descending aorta may comprise at least one of athoracic aorta, an abdominal aorta, and/or any branches thereof. Theintrathoracic vessels may also comprise at least one of a subclavianartery, an internal thoracic artery, a pericardiacophrenic artery, aright pulmonary artery, a right coronary artery, a brachiocephalictrunk, a pulmonary trunk, a left pulmonary artery, an anteriorinterventricular artery, and/or branches thereof. The intrathoracicvessels may also comprise at least one of an inferior thyroid artery, athyrocervical trunk, a vertebral artery, a right bronchial artery, asuperior left bronchial artery, an inferior left bronchial artery,aortic esophageal arteries, and/or branches thereof.

In some aspects, the intrathoracic vessels may also comprise at leastone of a right internal jugular vein, a right brachiocephalic vein, asubclavian vein, an internal thoracic vein, a pericardiacophrenic vein,a superior vena cava, a right superior pulmonary vein, a leftbrachiocephalic vein, a left internal jugular vein, a left superiorpulmonary vein, an inferior thyroid vein, an external jugular vein, avertebral vein, a right highest intercostal vein, a 6th rightintercostal vein, an azygos vein, an inferior vena cava, a left highestintercostal vein, an accessory hemiazygos vein, a hemiazygos vein,and/or branches thereof.

In some aspects, the subthoracic vessels may comprise at least one ofrenal arteries, inferior phrenic arteries, a celiac trunk with commonhepatic, left gastric and splenic arteries, superior suprarenalarteries, a middle suprarenal artery, an inferior suprarenal artery, aright renal artery, a subcostal artery, 1st to 4th right lumbararteries, common iliac arteries, an iliolumbar artery, an internal iliacartery, lateral sacral arteries, an external iliac artery, a testicular(ovarian) artery, an ascending branch of deep circumclex iliac artery, asuperficial circumflex iliac artery, an inferior epigastric artery, asuperficial epigastric artery, a femoral artery, a ductus deferens andtesticular artery, a superficial external pudendal artery, a deepexternal pudendal artery, and/or branches thereof. The subthoracicvessels may also comprise at least one of a superior mesenteric artery,a left renal artery, an abdominal aorta, an inferior mesenteric artery,colic arteries, sigmoid arteries, a superior rectal artery, 5th lumbararteries, a middle sacral artery, a superior gluteal artery, umbilicaland superior vesical arteries, an obturator artery, an inferior vesicaland artery to ductus deferens, a middle rectal artery, an internalpudendal artery, an inferior gluteal artery, a cremasteric, pubic(obturator anastomotic) branches of inferior epigastric artery, a leftcolic artery, rectal arteries, and/or branches thereof.

In some aspects, the lateral thoracic vessels may comprise at least oneof humeral arteries, a transverse cervical artery, a suprascapularartery, a dorsal scapular artery, and/or branches thereof. The lateralthoracic vessels may also comprise at least one of an anteriorcircumflex humeral artery, a posterior circumflex humeral artery, asubscapular artery, a circumflex scapular artery, a brachial artery, athoracodorsal artery, a lateral thoracic artery, an inferior thyroidartery, a thyrocervical trunk, a subclavian artery, a superior thoracicartery, a thoracoacromial artery, and/or branches thereof.

In some embodiments, the delivery system can include an expandableoccluding device (e.g., stent) configured to be placed across ananeurysm. The occluding device can be delivered through the distalportion of the catheter, out a distal tip assembly, and into thevasculature adjacent an aneurysm in, for example, the middle cerebralartery. A proximal portion of the catheter can remain partially orentirely within a guiding catheter during delivery, and an intermediateportion, taper portion, and distal portion of the catheter can extenddistally of the guiding catheter. The occluding device can be releasedat the target location and can be used to occlude blood flow into theaneurysm. The catheter can be used to reach target locations (e.g.,aneurysms) located elsewhere in the body as well, include but notlimited to other arteries, branches, and blood vessels such as thosedescribed above.

The apparatus and methods discussed herein are not limited to thedeployment and use of an occluding device or stent within the vascularsystem but may include any number of further treatment applications.Other treatment sites may include areas or regions of the body such asorgan bodies.

Although the detailed description contains many specifics, these shouldnot be construed as limiting the scope of the subject technology butmerely as illustrating different examples and aspects of the subjecttechnology. It should be appreciated that the scope of the subjecttechnology includes other embodiments not discussed in detail above.Various other modifications, changes and variations may be made in thearrangement, operation and details of the method and apparatus of thesubject technology disclosed herein without departing from the scope ofthe present disclosure. Unless otherwise expressed, reference to anelement in the singular is not intended to mean “one and only one”unless explicitly stated, but rather is meant to mean “one or more.” Inaddition, it is not necessary for a device or method to address everyproblem that is solvable by different embodiments of the disclosure inorder to be encompassed within the scope of the disclosure.

What is claimed is:
 1. A stent delivery system, comprising: a coremember having a distal segment; and first and second restraints coupledto the core member distal segment and axially spaced apart from eachother to provide an axial gap, the first and second restraints eachhaving an outer profile that tapers radially inwardly; a stentengagement component rotatably coupled to the core member between thefirst and second restraints.
 2. The system of claim 1, furthercomprising a stent extending over at least one of the first or secondrestraints.
 3. The system of claim 2, wherein the system is configuredto permit the core member to bend in a curved path without causing thefirst and second restraints to compress the stent against an inner wallof the catheter.
 4. The system of claim 2, wherein the system isconfigured to permit the core member to bend in a curved path withoutcausing the first and second restraints to contact an inner surface ofthe stent.
 5. The system of claim 1, wherein the first and secondrestraints each have an outer profile that tapers radially inwardly indirections away from each other.
 6. The system of claim 1, wherein thefirst restraint is positioned distally of the second restraint.
 7. Thestent delivery system of claim 1, wherein the stent engagement componentcomprises an engagement member configured to cooperate with an innerwall of the catheter to grip the stent to move the stent within thecatheter.
 8. The system of claim 1, wherein the delivery systemcomprises a first radiopaque marker and the catheter comprises a secondradiopaque marker longitudinally movable relative to the firstradiopaque marker, and wherein the system is configured such thatlongitudinally aligning the first and second radiopaque markers achievesa pre-release position beyond which additional distal advancement of thecore member permits release of the stent from the delivery system. 9.The system of claim 8, wherein the first restraint comprises the firstradiopaque marker and a distal portion of the catheter comprises thesecond radiopaque marker.
 10. The stent delivery system of claim 8,wherein the second radiopaque marker is positioned at the catheterdistal end, and the advancing comprises longitudinally aligning thefirst restraint with the catheter distal end.
 11. A stent deliverysystem, comprising: a catheter having a lumen; a core member having adistal segment and configured to be received within the catheter lumen;first and second restraints coupled to the core member distal segmentand axially spaced apart from each other to provide an axial gap, thefirst and second restraints each having an outer profile that tapersradially inwardly; and a stent engagement member rotatably coupled tothe core member distal segment in the axial gap.
 12. The system of claim11, wherein the first and second restraints have maximum outercross-sectional profiles that are less than a maximum diameter of thestent engagement member.
 13. The system of claim 11, wherein the firstand second restraints have different maximum outer cross-sectionalprofiles.
 14. The system of claim 11, further comprising (i) a thirdrestraint spaced apart from the first and second restraints andproviding a second axial gap and (ii) a second stent engagement memberrotatably coupled to the core member distal segment in the second axialgap.
 15. The system of claim 11, wherein the delivery system comprises afirst radiopaque marker, the catheter comprises a second radiopaquemarker, the first and second radiopaque markers being longitudinallymovable relative to each other and longitudinally alignable with eachother such that the system achieves a pre-release position beyond whichadditional distal advancement of the core member permits release of astent from the delivery system.
 16. The system of claim 15, wherein thefirst restraint comprises the first radiopaque marker, and a distalportion of the catheter comprises the second radiopaque marker.
 17. Thesystem of claim 16, wherein the second radiopaque marker is positionedat the catheter distal end.